Twenty students and three teachers on a field trip were killed by a fire that tore through their bus in Pathum Thani on Tuesday.

Sixteen students and three teachers were sent to nearby hospitals for treatment.

The bus was carrying 38 students, from Kindergarten 2 to Matthayom 3, and six teachers from Wat Khao Praya Sangkharam school in Lam Sak district of Uthai Thani.

Police confirmed 23 students and three teachers died, trapped in the fire on the bus.

Nineteen people were rescued. They were taken to local hospitals.

Rescue workers said 15 of the dead passengers were primary school pupils and six were high schoolers. Six kindergarten pupils on the bus survived.

Police were told about noon that a bus was on fire on an inbound lane of Vibhavadi Rangsit and Phahon Yothin roads, near the Zeer Rangsit shopping centre in Pathum Thani. 

Rescuers said the bus's front left tyre had blown out and the wheel caught fire. The driver lost control, the bus hit the road barrier and the flames rapidly spread up and throughout the vehicle.

The bus was the second of a three-bus fleet taking students on a one-day educational trip.

The bus belonged to Chinnaboot Tour, based in Sing Buri.

The driver of the bus, identified as Samarn Chankut, initially fled the scene and his mobile phone was turned off, police said.

It was later reported that he had fled to Ang Thong but then turned himself in to police there on Tuesday night. He is now being held at Khu Khot police station in Pathum Thani.

Prime Minister Paetongtarn Shinawatra sent condolence messages to the families of those who lost their lives or were injured and said the government would be cover medical costs and provide financial aid to the victims and the bereaved families.