Around 25 people are feared dead after a school bus carrying students and teachers on a field trip caught fire near Bangkok on Tuesday, with 16 others hospitalized, according to Thai authorities.

Police could not immediately confirm the number of injuries or deaths but Interior Minister Anutin Charnvirakul told reporters about 25 people were believed to have been killed, without elaborating.

Sixteen students and three teachers were sent to a hospital for treatment, Transport Minister Suriya Juangroongruangkit said, adding the causes of the incident were still being investigated.

Early images posted on social media and carried by local news outlets showed thick grey smoke pouring out of the bus, parts of which were still on fire.

The blaze was later extinguished. A Reuters photographer saw fire trucks, police and rescue vehicles parked around the blackened vehicle, with a cluster of firefighters at the entrance.

Prime Minister Paetongtarn Shinawatra said the students were on a field trip from the province of Uthai Thani, about 250 kilometers (155 miles) north of the capital.

"As a mother, I would like to express my deepest condolences to the families," she said in a social media post on X.