BANGKOK — A senior high school student has died after an extinguisher exploded during a fire drill at his campus in Thailand.

Twenty-one others at Rajavinit Mathayom School in Bangkok were injured in Friday's incident, said the city's governor. Seven were taken to hospital.

The explosion had sent the extinguisher flying towards the victim, who was about 10 metres away.

Rescuers said the extinguisher may have been defective because of sun or heat exposure.

The dead student was in his final year of school. His age has not been confirmed.

Police have been investigating the cause of the incident, cordoning off the scene which remained scattered with debris.

Officials added that the extinguishers used in the drill have all been sent to the police's forensics division.

The exploding cannister contained carbon dioxide, according to the Ruamkatanyu Foundation, the rescue organisation on the scene.

The extinguishers are usually refilled with chemicals when empty, but "how and where they were refilled must be investigated, and safety valves must be checked", said the city's police chief.

The school is located in the Dusit district, alongside many government offices.

Ministry of Education officials have also been sent to the school to determine what happened, permanent secretary Atthaphon Sangkhawasee said.

He expressed condolences to the relatives of the dead student, adding that the ministry would assist and compensate those affected, according to The Nation. — BBC