01:16 More Bad Air Days This Weekend in the West Ongoing wildfires in the West have caused major air quality issue. Meteorologist Danielle Banks explains the 3 big reasons the region will see bad air this weekend.

At a Glance Deadly forest fires have killed dozens in Portugal.

Authorities came under mounting criticism for not doing more to prevent the tragedy.

Scorching weather, with temperatures surpassing 104 degrees, as well as strong winds fueled the blazes. Cooler overnight temperatures Monday helped more than 1,000 soldiers and firefighters in Portugal help bring some blazes under control in Portugal, where the death toll rose to 63.

However, some of the wildfires are still racing through inaccessible parts of hill ranges about 90 miles northeast of Lisbon, while authorities come under mounting criticism for not doing more to prevent the tragedy.

Reinforcements, including more water-dropping planes from Spain, France and Italy, were due to arrive as part of a European Union cooperation program, officials said.

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However, giant clouds of smoke were preventing the deployment of water-dropping aircraft on wildfires in the central region of the country where dozens died in runaway flames, officials said.

Portugal is observing three days of national mourning after the deaths Saturday night around the town of Pedrogao Grande, about 90 miles north of Lisbon, which is by far the deadliest on record. The latest death was that of an injured firefighter, according to the league of Portuguese firefighters on its website.

Scorching weather, with temperatures surpassing 104 degrees, as well as strong winds and dry woodland after weeks with little rain fueled the blazes. The fire area is covered in dense woodland over steep hills.

The catastrophe is believed to have been initially caused by a dry thunderstorm, an environmental phenomenon blamed for starting wildfires worldwide. In it, falling rain evaporates before reaching the ground because of high temperatures, but lightning from the high cumulonimbus clouds reaches the ground. With no rain to wet the land, fires start and are fanned more quickly by gusty winds.

Portuguese police detectives said forestry guards and investigators were able to determine the tree struck by lightning on Saturday during the dry thunderstorm in the Pedrogao Grande area. The tree was in the village of Escalos Fundeiros, said police chief Almeida Rodrigues.

The regional prosecutor has ordered a criminal investigation into the fire's causes but the probe could be dropped if the police version is fully confirmed.

Meanwhile, Portugal's leading environmental lobby group, Quercus, issued a statement Monday blaming the blazes on "forest management errors and bad political decisions" by governments over recent decades.

The association rebuked authorities for allowing the planting of huge swathes of eucalyptus, the country's most common and most profitable species - but one that's often blamed for stoking blazes.

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Emergency services have been criticized for not closing a road where 47 of the deaths occurred as people fled the flames Saturday night. The government has acknowledged that the huge fires occasionally led to a breakdown in communications.

Wildfires are an annual scourge in Portugal. Between 1993 and 2013, Portugal recorded the highest annual number of forest fires in southern Europe, according to a report last year by the European Environment Agency.

The government announced a raft of new measures against wildfires in March. They included restrictions on eucalyptus plantations and a simplified and cheaper program of property registration that seeks to ascertain which land is being neglected.

Not all of those reforms have come into legal force yet.

Statistics show that 35 percent of Portugal is covered by woodland. The forest industry, especially the production of paper pulp, accounts for around 3 percent of GDP.