The bus was running on compressed gas and the crash ignited its fuel tanks, said a rescue worker.
A devastating fire tore through a Thai bus carrying 44 students and teachers on a school trip Tuesday, officials said, with up to 25 feared dead.
Prime Minister Paetongtarn Shinawatra said there were fatalities and offered condolences to the victims' families.
Transport minister Suriya Jungrungreangkit said the number of fatalities was not clear but 25 people were unaccounted for after the blaze.
"Initial reports said there are 44 on board, 38 students and six teachers. As far as we know now, three teachers and 16 students got out," he told reporters.
"For those still missing, we are not clear yet."
The bus was carrying students from Uthai Thani province when a tyre burst on a highway in a northern Bangkok suburb, sending the vehicle crashing into a barrier, a rescue worker said in footage broadcast on local TV.
The bus was running on compressed gas and the crash ignited its fuel tanks, the rescue worker said.
Video footage from the scene showed flames engulfing the bus as it burned under an overpass, huge clouds of dense black smoke billowing into the sky.
"I have learned of the fire on a bus carrying students from Uthai Thani... resulting in deaths and injuries," Paetongtarn wrote on X, formerly Twitter.
"As a mother, I would like to express my deepest condolences to the families of the injured and deceased."
The blaze has been put out but rescue workers have had to wait for the bus to cool down before searching it for bodies, a rescue worker said.
Thailand has one of the worst road safety records in the world, with unsafe vehicles and poor driving contributing to the high annual death count.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
