The bus was carrying 44 passengers from central Uthai Thani province for a school trip in Ayutthaya and Nonthaburi provinces, Transport Minister Suriya Jungrungruengkit 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. Bodies were still inside the bus hours after the fire.

The students 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 because they had not finished investigating the scene. He said the driver survived but appeared to have fled and could not yet be found.

Anutin had earlier said 25 were feared dead, but Piyalak Thinkaew, a rescuer of the Ruamkatanyu Foundation told reporters later that two more survivors had been found, reducing the number of those still missing to 23 — three teachers and 20 students.

Rescuers and officials were able to access the bus hours after the fire was put out. Piyalak said they were still unable to identify the bodies, most of which were found in the middle and back seats, leading them to assume that the fire started at the front of the bus.

Thai media reports and rescuers said the bus 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 Suriya that the fire likely started after one of the tires exploded and the vehicle scraped against a road barrier.

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

The patRangsit Hospital, which is located near the scene, said in a news conference that it admitted three young girls, one of whom suffered burns to the face, mouth and eye.