Cracks are emerging around the volcano that spewed lava and plumes of ash near the Philippine capital on Sunday, raising the likelihood of an imminent major eruption.

That's the verdict of experts at the Philippine Institute of Volcanology and Seismology, or Phivolcs, which said the threat level from the Taal volcano south of Manila remained at level 4 on Tuesday – one short of an active eruption.

At a news conference, Phivolcs experts explained that while surface activity had slowed, there were clear indications that magma – molten rock in the Earth’s crust – continued to rise up from below. The signs, said chief scientist Maria Antonia Bornas, were similar to those in a major 1911 event "before it progressed into a climactic or explosive eruption". The 1911 eruption killed about 1,500 people.

Successive strong earthquakes – about 50 volcanic tremors – were detected over eight hours on Tuesday. This also indicated rising magma, Bornas said. The message to the public, she said, was that the danger had not necessarily eased just because surface activity had slowed, and the appearance of fissuring cracks was particularly worrying.

Nonetheless, Manila's mayor announced that schools, which have been suspended since Sunday, would reopen on Wednesday, and while ashfall affected more than 500 domestic and international flights, the main airport at Manila has been back in operation since Monday afternoon.

Philippines Taal volcano: Eruption in photos Show all 44 1 /44 Philippines Taal volcano: Eruption in photos Philippines Taal volcano: Eruption in photos Lightning strikes as a column of ash surrounds the crater of Taal Volcano as it erupts in Tagaytay, Philippines Getty Philippines Taal volcano: Eruption in photos Mandatory Credit: Photo by Domcar C Lagto/PACIFIC P/SIPA/REX (10524315i) Lightning streak over Batangas as Taal Volcano continue its eruption on Sunday evening. Phivolcs reminded the public that the volcano's main crater was "strictly off limits" due to sudden steam explosions and the possible release of high concentrations of lethal volcanic gases. Residents of towns near Taal Volcano are being taken to safer ground following increasing volcanic activity, a disaster-mitigation official said. Taal volcano erupts, Philippines - 12 Jan 2020 Domcar C Lagto/PACIFIC P/SIPA/REX Pacific Press via Sipa/Rex Philippines Taal volcano: Eruption in photos Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Getty Philippines Taal volcano: Eruption in photos Mandatory Credit: Photo by Domcar C Lagto/PACIFIC P/SIPA/REX (10524315a) Lightning streak over Batangas as Taal Volcano continue its eruption on Sunday evening. Phivolcs reminded the public that the volcano's main crater was "strictly off limits" due to sudden steam explosions and the possible release of high concentrations of lethal volcanic gases. Residents of towns near Taal Volcano are being taken to safer ground following increasing volcanic activity, a disaster-mitigation official said. Taal volcano erupts, Philippines - 12 Jan 2020 Domcar C Lagto/PACIFIC P/SIPA/REX Pacific Press via Sipa/Rex Philippines Taal volcano: Eruption in photos People take photos of a phreatic explosion from the Taal volcano as seen from the town of Tagaytay in Cavite province, southwest of Manila AFP Philippines Taal volcano: Eruption in photos Billows of smoke with lightning is seen from the eruption Mandatory Credit: Photo by Hero Robles/Pacific Press via ZUMA Wire/REX (10523925d) Billows of smoke with lightning is seen from the eruption of Taal Volcano. Taal Volcano erupts, Philippines - 12 Jan 2020 The Taal Volcano in the central Philippines boomed to life on Sunday, spilling ash and causing evacuations in nearby communities -- and officials warn that a more powerful eruption is imminent. Taal Volcano is located on the island of Luzon and is the country's second most active volcano. Hero Robles/Pacific Press via ZUMA Wire/REX Pacific Press via Zuma Wire/Rex Philippines Taal volcano: Eruption in photos Residents stand lakeside as the volcano erupts behind them TALISAY, PHILIPPINES - JANUARY 12: Residents stand near a lakeside as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos A family rides their motorcycle through clouds of ash as they evacuate to safer grounds A family rides their motorcycle through clouds of ash as they evacuate to safer grounds as Taal volcano in Tagaytay, Cavite province, southern Philippines on Monday, Jan. 13, 2020. Red-hot lava is gushing from the volcano after a sudden eruption of ash and steam that forced residents to flee and shut down Manilaâ€™s airport, offices and schools. (AP Photo/Aaron Favila) Aaron Favila AP Philippines Taal volcano: Eruption in photos Lightning streak over Batangas Mandatory Credit: Photo by Domcar C Lagto/PACIFIC P/SIPA/REX (10524315g) Lightning streak over Batangas as Taal Volcano continue its eruption on Sunday evening. Phivolcs reminded the public that the volcano's main crater was "strictly off limits" due to sudden steam explosions and the possible release of high concentrations of lethal volcanic gases. Residents of towns near Taal Volcano are being taken to safer ground following increasing volcanic activity, a disaster-mitigation official said. Taal volcano erupts, Philippines - 12 Jan 2020 Domcar C Lagto/PACIFIC P/SIPA/REX Pacific Press via Sipa/Rex Philippines Taal volcano: Eruption in photos The tiny volcano near the Philippine capital draws many tourists for its picturesque setting, however as it belched steam, ash and rocks in a huge plume thousands were forced to flee and officials to temporarily suspend flights AP Philippines Taal volcano: Eruption in photos Ashfall after the eruption of the Taal volcano Ashfall after the eruption of the Taal volcano is seen in Tagaytay City, Cavite, Philippines January 13, 2020 in this picture obtained from social media. JEROME AUSTRIA ABUAN /via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. JEROME AUSTRIA ABUAN Jerome Austria Abuan via Reuters Philippines Taal volcano: Eruption in photos Villagers evacuate epa08122662 Villagers evacuate during Taal Volcano's eruption in Talisay, Batangas, Philippines, 12 January 2020. Thousands of people have been ordered to evacuate as authorities in the Philippines raised the alert due to increased activity of Taal volcano, located on an island near Manila. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the alert level from 1 to 3 - on a scale of 5 - after an increase in activity in the crater resulted in an eruption spewing steam and ash up to one-kilometer-high. EPA/FRANCIS R. MALASIG FRANCIS R. MALASIG EPA Philippines Taal volcano: Eruption in photos Taal volcano erupts The errupting Taal Volcano is seen from Tagaytay City, Philippines, January 13, 2020. REUTERS/Eloisa Lopez ELOISA LOPEZ Reuters Philippines Taal volcano: Eruption in photos Lightning flashes as Taal Volcano erupts The Philippine Institute of of Volcanology and Seismology has raised the alert level to four out of five, warning that a hazardous eruption could take place anytime AP Philippines Taal volcano: Eruption in photos A dog left in a garage covered with ashes barks nearby the erupting Taal Volcano A dog left in a garage covered with ashes barks nearby the erupting Taal Volcano in Talisay, Batangas, Philippines, January 13, 2020. REUTERS/Eloisa Lopez ELOISA LOPEZ Reuters Philippines Taal volcano: Eruption in photos A volcanic lightning caused by eruption A volcanic lightning caused by eruption is seen over Tagaytay City, Cavite province, Philippines January 12, 2020 in this picture obtained from social media. @DERRICKQUIBAEL/via REUTERS ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. @DERRICKQUIBAEL @DERRICKQUIBAEL via REUTERS Philippines Taal volcano: Eruption in photos Ash from the Taal volcano in the air, with a church in the foreground This handout photo taken and received on January 12, 2020 courtesy of Renz Lejarso Guevara shows ash from the Taal volcano (not pictured) in the air, as seen against a church in the foreground in the town of Taal in Batangas province south of Manila. - A volcano near the Philippine capital Manila spewed a massive cloud of ash into the sky on January 12, forcing the precautionary evacuation of thousands of residents, authorities said. (Photo by Handout / Courtesy of Renz Lejarso Guevara / AFP) / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / Courtesy of Renz Lejarso Guevara" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS --- NO ARCHIVE --- (Photo by HANDOUT/Courtesy of Renz Lejarso Guevara/AFP via Getty Images) HANDOUT Renz Lejarso Guevara/AFP Philippines Taal volcano: Eruption in photos A column of ash surrounds the crater of Taal Volcano TAGAYTAY, PHILIPPINES - JANUARY 12: A column of ash surrounds the crater of Taal Volcano as it erupts on January 12, 2020 as seen from Tagaytay city, Cavite province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to four out of five, warning that a hazardous eruption could take place anytime. (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos Residents stand lakeside as the volcano erupts behind them TALISAY, PHILIPPINES - JANUARY 12: Residents look on as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos Lightning strikes over Taal Volcano Lightning flashes as Taal Volcano erupts Sunday Jan. 12, 2020, in Tagaytay, Cavite province, outside Manila, Philippines. A tiny volcano near the Philippine capital that draws many tourists for its picturesque setting in a lake belched steam, ash and rocks in a huge plume Sunday, prompting thousands of residents to flee and officials to temporarily suspend flights. (AP Photo/Aaron Favila) Aaron Favila AP Philippines Taal volcano: Eruption in photos Residents walk along a road covered in ash mixed with rainwater TALISAY, PHILIPPINES - JANUARY 12: Residents walk along a road covered in ash mixed with rainwater as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos Lightning strikes over Taal Volcano epa08122218 A view of a lightning strike over Taal Volcano during an eruption, in Talisay, Batangas, Philippines, 12 January 2020. Thousands of people have been ordered to evacuate as the authorities in the Philippines raised the alert due to increased activity of Taal volcano, located on an island near Manila. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the alert level from 1 to 3 - on a scale of 5 - after an increase in activity in the crater resulted in an eruption spewing steam and ash up to one-kilometer-high. EPA/FRANCIS R MALASIG FRANCIS R MALASIG EPA Philippines Taal volcano: Eruption in photos Villagers take shelter inside a church during the eruption epa08122449 Villagers take shelter inside a church during an eruption of Taal Volcano, in Talisay, Batangas, Philippines, 12 January 2020. Thousands of people have been ordered to evacuate as authorities in the Philippines raised the alert due to increased activity of Taal volcano, located on an island near Manila. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the alert level from 1 to 3 - on a scale of 5 - after an increase in activity in the crater resulted in an eruption spewing steam and ash up to one-kilometer-high. EPA/FRANCIS R. MALASIG FRANCIS R. MALASIG EPA Philippines Taal volcano: Eruption in photos A volcanic lightning caused by eruption A volcanic lightning caused by eruption is seen over Tagaytay City, Cavite province, Philippines January 12, 2020 in this picture obtained from social media. @DERRICKQUIBAEL/via REUTERS ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES. @DERRICKQUIBAEL @DERRICKQUIBAEL via Reuters Philippines Taal volcano: Eruption in photos Taal volcano erupts A phreatic explosion from the Taal volcano is seen from the town of Tagaytay in Cavite province, southwest of Manila, on January 12, 2020. (Photo by Bullit MARQUEZ / AFP) (Photo by BULLIT MARQUEZ/AFP via Getty Images) BULLIT MARQUEZ AFP via Getty Philippines Taal volcano: Eruption in photos Lightning strikes over Taal Volcano TAGAYTAY, PHILIPPINES - JANUARY 12: Lightning strikes as a column of ash surrounds the crater of Taal Volcano as it erupts on January 12, 2020 as seen from Tagaytay city, Cavite province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to four out of five, warning that a hazardous eruption could take place anytime. (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos A policeman walks past a police vehicle covered in ash TALISAY, PHILIPPINES - JANUARY 12: A policeman walks past a police vehicle covered in ash mixed with rainwater as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos A fishing boat sails along a lake as Taal Volcano erupts TALISAY, PHILIPPINES - JANUARY 12: A fishing boat sails along a lake as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos A vehicle covered in ash TALISAY, PHILIPPINES - JANUARY 12: A vehicle covered in ash mixed with rainwater is seen as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos An ash column from erupting Taal Volcano looms over Tagaytay city epaselect epa08121804 An ash column from erupting Taal Volcano looms over Tagaytay city, Philippines, 12 January 2020. According to media reports, evacuations are underway as the volcano spewed ash as high as 100 meters into the sky. EPA/FRANCIS R. MALASIG FRANCIS R. MALASIG EPA Philippines Taal volcano: Eruption in photos Lightning strikes over Taal Volcano TAGAYTAY, PHILIPPINES - JANUARY 12: Lightning strikes as a column of ash surrounds the crater of Taal Volcano as it erupts on January 12, 2020 as seen from Tagaytay city, Cavite province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to four out of five, warning that a hazardous eruption could take place anytime. (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos A resident splashes water on a vehicle covered in ash TALISAY, PHILIPPINES - JANUARY 12: A resident splashes water on a vehicle covered in ash mixed with rainwater as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos Taal volcano spews ash and smoke People watch as the Taal volcano spews ash and smoke during an eruption in Tagaytay, Cavite province south of Manila, Philippines on Sunday. Jan. 12, 2020. A tiny volcano near the Philippine capital that draws many tourists for its picturesque setting in a lake belched steam, ash and rocks in a huge plume Sunday, prompting thousands of residents to flee and officials to temporarily suspend flights. (AP Photo/Bullit Marquez) Bullit Marquez AP Philippines Taal volcano: Eruption in photos A person on a canoe while the volcano spews ash TOPSHOT - A youth living at the foot of Taal volcano rides an outrigger canoe while the volcano spews ash as seen from Tanauan town in Batangas province, south of Manila, on January 13, 2020. - The Philippines was on alert January 13 for the "explosive eruption" of a volcano south of Manila, which officials said could be imminent after a massive column of ash forced a halt to flights at the capital's main airport. (Photo by Ted ALJIBE / AFP) (Photo by TED ALJIBE/AFP via Getty Images) TED ALJIBE AFP via Getty Philippines Taal volcano: Eruption in photos Residents walk along a road covered in ash mixed with rainwater TALISAY, PHILIPPINES - JANUARY 12: Residents walk along a road covered in ash mixed with rainwater as Taal Volcano erupts on January 12, 2020 in Talisay, Batangas province, Philippines. Local authorities have begun evacuating residents near Taal Volcano as it began spewing ash up to a kilometer high Sunday afternoon. The Philippine Institute of of Volcanology and Seismology has raised the alert level to three out of five, warning of the volcano's continued "magmatic unrest." (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos Taal volcano erupts A view of the Taal volcano eruption seen from Tagaytay, Philippines January 12, 2020 in this still image taken from social media video. Jon Patrick Laurence Yen via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES TPX IMAGES OF THE DAY JON PATRICK LAURENCE YEN JPL YEN via Reuters Philippines Taal volcano: Eruption in photos Lightning strikes over Taal Volcano epaselect epa08122217 A view of a lightning strike over Taal Volcano during an eruption, in Talisay, Batangas, Philippines, 12 January 2020. Thousands of people have been ordered to evacuate as the authorities in the Philippines raised the alert due to increased activity of Taal volcano, located on an island near Manila. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the alert level from 1 to 3 - on a scale of 5 - after an increase in activity in the crater resulted in an eruption spewing steam and ash up to one-kilometer-high. EPA/FRANCIS R MALASIG FRANCIS R MALASIG EPA Philippines Taal volcano: Eruption in photos A worker hoses down plants covered with mud and ash TOPSHOT - A worker hoses down plants covered with mud and ash after Taal volcano erupted, in Talisay town, Batangas province south of Manila on January 13, 2020. - Lava and broad columns of ash illuminated by lightning spewed from a volcano south of the Philippine capital on January 13, grounding hundreds of flights as authorities warned of a possible "explosive eruption". (Photo by Ted ALJIBE / AFP) (Photo by TED ALJIBE/AFP via Getty Images) TED ALJIBE AFP via Getty Philippines Taal volcano: Eruption in photos Residents evacuate Residents living near the erupting Taal Volcano evacuate from Lemery, Batangas, Philippines, January 13, 2020. ELOISA LOPEZ Reuters Philippines Taal volcano: Eruption in photos Taal volcano erupts Taal volcano continues to erupt in Lemery, Batangas, southern Philippines on Monday, Jan. 13, 2020. Red-hot lava gushed out of a volcano near the Philippine capital on Monday, as thousands of people fled the area through heavy ash. Experts warned that the eruption could get worse and plans were being made to evacuate hundreds of thousands. (AP Photo/Aaron Favila) Aaron Favila AP Philippines Taal volcano: Eruption in photos Taal Volcano erupts with a massive plume of ash and steam Mandatory Credit: Photo by Xinhua/REX (10524323b) The Taal Volcano erupts with a massive plume of ash and steam in Batangas Province Taal Volcano erupts, Philippines - 13 Jan 2020 Nearly 50,000 people living near a volcano on an island close to the Philippine capital have heeded official warning to evacuate as fears of an eruption grew, officials said on Monday. The Philippine Institute of Volcanology and Seismology increased the alert level for Taal Volcano in Talisay town in Batangas, approximately 66 km south of Manila, on Sunday to 4 on a scale of 5, indicating an increased prospect of a hazardous eruption 'within hours to days'. Xinhua/REX Xinhua/Rex Philippines Taal volcano: Eruption in photos Residents fleeing wait for a ride on the side of a highway LEMERY, PHILIPPINES - JANUARY 13: Residents fleeing Taal Volcano's eruption wait for a ride on the side of a highway on January 13, 2020 in Lemery, Batangas province, Philippines. The Philippine Institute of of Volcanology and Seismology raised the alert level to four out of five, warning that a hazardous eruption could take place anytime, as Manila's international airport suspended flights and authorities began evacuating tens of thousands of people from the area. (Photo by Ezra Acayan/Getty Images) Ezra Acayan Getty Philippines Taal volcano: Eruption in photos People travel along a road covered in ash epa08123994 People travel along a road covered in ash deposits, a day after the eruption of Taal Volcano, in Agoncillo town in Batangas province, Philippines, 13 January 2020. Thousands of people have been ordered to evacuate as authorities in the Philippines raised the alert status, due to the increased activity, of the Taal Volcano, located near Manila. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) raised the alert level from one to three, before raising it to four. EPA/ROLEX DELA PENA ROLEX DELA PENA EPA Philippines Taal volcano: Eruption in photos A massive plume of ash and steam erupts A small volcano near the Philippine capital of Tagaytay that draws tourists for its picturesque setting in a lake erupts with a massive plume of ash and steam Sunday, Jan. 12, 2020, prompting the evacuation of tens of thousands of people and forcing Manila's international airport to shut down. The Philippine Institute of Volcanology and Seismology said Taal Volcano in Batangas province south of Manila blasted steam, ash and pebbles up to 10 to 15 kilometers (6 to 9 miles) into the sky in a dramatic escalation of its growing restiveness, which began last year. (Lester Matienzo via AP) Lester Matienzo AP

The perception that the crisis was over represented a major challenge to agencies in the most-affected province of Batangas, said Phivolcs chief Renato Solidum.

"We have to make sure that people understand and, of course, government, that this is not an activity that will just be in a short while," he said.

Tens of thousands of people have fled villages darkened and blanketed by heavy ash from Taal, and government work was also suspended in a number of towns and cities over ash-related health risks. The official count of evacuees stood at just over 40,000 as of Tuesday evening, though that number is expected to rise.

And Save the Children estimated that 21,000 children alone had been evacuated from the 14km danger zone identified by the Philippines government.

The charity said it was "deeply concerned" for children who have been forced to leave their homes. They are missing out on school, and facing hunger and disease in "cramped and unsanitary" evacuation centres.

Jerome Balinton, of the Save the Children Philippines, said the children "have no idea when or even if they will be able to return to their homes".

He told The Independent in a statement: “Our humanitarian team have just visited an arena now doubling up as an evacuation centre and it was heart-breaking.

"More than 900 people are sleeping on the cold, hard surface without mats. Due to sudden evacuation, people were not able to bring blankets, hygiene essentials, mosquito nets, and supplies for babies such as diapers."

One Philippines NGO donated 3,000 pollution masks to be distributed by the armed forces to affected regions, according to local media reports.

Balay Mindanaw brought 25 crates full of N95 filter face masks to Batangas after hearing reports that supplies in local markets had run out, manager Leonardo Bautista told ABS-CBN.

President Rodrigo Duterte visited Batangas on Tuesday, after it was declared a disaster zone so that emergency funds could be more quickly distributed.

Accompanied by top disaster-response officials and cabinet members, he reportedly offered his prayers "to prevent an eruption" and promised the national government would help with the cleanup and reconstruction of the devastated province once the ashfall ends.