A devastating fire tore through a Thai bus carrying 44 children 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.
The bus was one of three carrying children -- ranging from kindergarten age to around 13 or 14 years old -- from Wat Khao Phraya Sangkharam school in the northern province of Uthai Thani.
Transport Minister Suriya Juangroongruangkit said the number of dead 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 disaster began when a tyre burst on a highway in a northern Bangkok suburb around 12:30 pm (0530 GMT), sending the bus crashing into a barrier and bursting into flames, rescuers 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.
Rescue workers put up screens to shield firefighters and investigators as they began recovering bodies from the charred wreckage.
"Some of the bodies we rescued were very, very small. They must have been very young in age," Piyalak Thinkaew, who is leading the search, told reporters at the scene, adding that the fire started at the front of the bus.
"The kids' instinct was to escape to the back so the bodies were there," he said.
The bodies are so badly charred that it is hard to identify them, he said.
Some of the children who escaped suffered horrific burns to their faces, mouths and eyes, doctors treating them told local media.
"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."
Meechai Sa-ard, a motorbike taxi driver, heard the noise of the incident from a kilometre (0.6 miles) away.
"There was smoke everywhere. Poor children, I heard they were very little," he told AFP.
"I was hoping that god would be kind so that the rain could put the fire out and the kids would survive."
The blaze has been put out but rescuers 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 toll.
Around 20,000 people are killed every year on the kingdom's roads, according to the World Health Organization (WHO) -- more than 50 a day on average.
The economic losses caused by traffic deaths and injuries amounted to around $15.5 billion in 2022 -- more than three percent of GDP -- the WHO says.
