Tagaytay, Philippines — 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.

Clouds of ash blew north from the Taal volcano, reaching Manila, the bustling capital, and forcing the shutdown of the country's main airport, with more than 500 flights canceled so far.

There were no reports of casualties or major damage from the eruption, which began Sunday.

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Some government offices, schools and many businesses in a wide swath of towns and cities were closed Monday to avoid health risks posed by the ashfall.

Police said more than 13,000 villagers had moved to evacuation centers in the hard-hit province of Batangas and nearby Cavite province, but officials expect the number to swell with hundreds of thousands more being brought out of harm's way.

Residents living near the erupting Taal Volcano evacuate from Lemery, Batangas, Philippines, ON January 13, 2020. ELOISA LOPEZ / REUTERS

The current evacuation numbers are likely higher since local authorities are busy helping displaced people before notifying the national agency collating the figures. Some residents couldn't move out of ash-blanketed villages due to a lack of transport and poor visibility, while others were refusing to leave their homes and farms.

Large numbers of displaced villagers worried about the homes, farms and cattle they left behind and the uncertain future they face.

Several planes stranded at Manila's airport may be allowed to take off Monday once they're cleaned of ash and authorities are sure an easterly shift in ash-laden wind away from the capital wouldn't revert, airport general Ed Monreal told a news conference. The airport can't accommodate incoming flights until stranded aircraft fly out and free up parking bays, he said.

President Rodrigo Duterte's aircraft was able to land Monday, however, after his flight from his home city of Davao in the south was delayed Sunday by the eruption, his spokesman said.

Plumes of smoke and ash rise as the Taal volcano erupts Sunday, January 12, 2020, outside Manila, Philippines. Aaron Favila / AP

Taal had been restive for months until it suddenly rumbled back to life Sunday, blasting steam, ash and pebbles 6 to 9 miles into the sky, according to the Philippine Institute of Volcanology and Seismology. The lava spurting from the volcano's vents Monday was falling into the lake surrounding the crater.

The government volcano-monitoring agency raised the danger level around Taal three notches to level 4, indicating "an imminent hazardous eruption." Level 5, the highest, means a hazardous eruption is underway and could affect a larger area with high-risk zones that would need to be cleared of people, said Renato Solidum, who heads the institute.

Ma. Antonio Bornas, the agency's chief volcanologist, said Taal spurted fountains of lava early Monday while its ash and steam ejections slightly eased. It's hard to tell when the eruption will stop, she said, citing the volcano's similar restiveness in the 1970s that lasted for about four months.

With the ashfall easing Monday morning, some residents began to shovel away inches of ash that covered everything from homes to cars and roads in Tagaytay, a popular upland resort city on a ridge that overlooks the small but picturesque volcano in the middle of a crater lake. Many of the city's restaurants and coffee shops, however, were closed, its main road covered in volcanic ash.

The volcanology institute reminded the public that the small island where the volcano lies is a "permanent danger zone," although fishing villages have existed there for years. It stressed that the "total evacuation" of people on the volcano island and lakeshore "at high risk to pyroclastic density currents and volcanic tsunami within a 14-kilometer (9-mile) radius from Taal."

Authorities continue to detect swarms of earthquakes, some of them felt with rumbling sounds, and a slight inflation of portions of the 1,020-foot volcano, officials said, advising residents to stay indoors and wear masks and goggles if they must venture outside.

One of the world's smallest volcanoes, Taal is among two dozen active volcanoes in the Philippines, which lies along the so-called Pacific "Ring of Fire," a seismically active region that is prone to earthquakes and volcanic eruptions.