Fire crews spray water on forest fires which have ravaged Chiang Mai in northern Thailand.
The blazes which began on March 23 have spread across the region destroying more than 400 hectares of forest.
Footage from Saturday afternoon (March 28) shows police, army, rescue volunteers and firemen trawling through the forest to fight the flames.
Thailand's environment minister Varawut Silpa-archa said on Monday (March 30) some of the fires may have been started deliberately.
During the period from January to April farmers in Southeast Asia use an agricultural process known as 'slash and burn' to clear the land of waste crops to prepare for the next season.
Officials also believe that some residents are deliberately starting fires to cause panic or farmers have left camp fires which have spread through vegetation.
The environment chief said: "Some of the fires at Doi Suthep-Pui National Park in Chiang Mai were the result of villagers burning forest to aid foraging.
But we found some people deliberately set fires to create mayhem.
We do not know why they wished to do this.''
Prime Minister Prayut Chan-o-cha is understood to be ''deeply concerned'' about forest fires in the northern region.
More than 3,000 ministry employees have been drafted in to help tackle the blazes.
The Doi Suthep-Pui national park chief officer said the main causes were camp fires started by locals who had been hunting and foraging in the area.
He said: "Most of the fires started in high on the mountain where people go hunting.
They set a camp fire and it can spread quickly.
"We have to keep people under control.
Sometimes they will violate the rules and burn their land to prepare the soil for farming next season."
The provincial governor Charoenrit Sanguansat said the government office is taking the issue seriously to stop the pollution.
He said: "With the cooperation from the police we have caught and charged 315 hunters and locals for causing fires.
"The fire has caused air pollution that affects people lives across the province and we are trying our best to control it."