Forest fires ripped through mountains amid worsening air quality in Thailand.

The blaze engulfed swathes of woodland in the Doi Pui area of Chiang Rai province on April 17, and threatened to spread to TV transmission towers of local networks.

Volunteers and firefighters battled the raging flames and set up firebreaks on the mountain, but tackling the inferno was made more difficult due to the steep and remote terrain.

Local media reported that authorities had identified suspects responsible for the blaze, which they believe started from burning waste.

Authorities are working to extinguish the fires, which are exacerbating the haze problem currently gripping Thailand. As of April 17, there were 178 hot spots detected in Chiang Rai.

On Tuesday, Chiang Rai had the worst air quality in the world, with a level of 196 from Swiss air monitor IQAir. The service recorded 142.1 micrograms of the deadly PM2.5 particles in the air, 28.4 times the safe level advised by the World Health Organization (WHO).

Scientists found that smog is at its worst in the country when farmers burn waste crops to cheaply clear their land between late October and April. It has been worsened in recent years by rising demand for food and agro-business lobbyists that can stifle the government's control over farmers.

The seasonal lack of wind and rain, combined with a winter low-pressure system in which cold air is trapped closer to the ground by warm air above – hampers the pollution from being dispersed naturally by wind.

The Thai government has been criticised for failing to tackle the country's air pollution crisis, with bizarre measures such as spraying water into the air and giant purifiers having no impact.