The incident occurred on Tuesday on the outskirts of the capital Bangkok.

The bus was carrying 44 passengers from central Uthai Thani province for a school trip in Ayutthaya and Nonthaburi provinces, transport minister Suriya Juangroongruangkit told reporters at the scene.

Videos posted on social media showed the entire bus engulfed in fire with huge plumes of black smoke pouring out as it stood on the side of the road.

The pupils on the bus were reported to be in elementary and junior high school.

Interior minister Anutin Charnvirakul said officials could not yet confirm the number of fatalities, but based on the number of survivors, he said 25 people are feared dead.

He added the driver survived but appeared to have fled and could not yet be found.

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Thai media reports and rescuers said it was heading to Nonthaburi when the fire started around noon in Pathum Thani province, a northern suburb of the capital.

A rescuer at the scene told the transport minister that the fire likely started after one of the tyres exploded and the vehicle scraped against a road barrier.

Prime Minister Paetongtarn Shinawatra offered her condolences in a post on X, saying the government would take care of medical expenses and compensate the victims' families.

Rescue group Hongsakul Khlong Luang 21 posted on Facebook that they found at least 10 bodies on the bus. The group said at least 19 people survived the fire.