Bangkok governor Chadchart Sittipunt on Friday expressed condolences to the victims and families after an explosion at a school killed one student and injured more than 20 at Rajavinit Mathayom School in Bangkok’s Dusit district on Friday morning.

The death and injuries occurred when a fire extinguisher exploded during a fire drill.

Chadchart said after visiting the site he learned that 21 students suffered minor injuries. Five were sent to Vajira Hospital and two to BMA General Hospital.

The governor said the drill was organised by the school and Sam Sen fire station to teach students about fire safety. It is the first drill to ever be held at the school.

“The drill was scheduled in three rounds. During the second round, one of the 14 fire extinguishers exploded, fatally injuring the student who sat around 10 metres away,” he said.

Chadchart said the fire extinguisher that exploded contained carbon dioxide, which has a pressure of 800-1,200 PSI, far higher than chemical extinguishers at 100 PSI.

“CO2 canisters are often used during the drill as the gas does not spread very far and quickly dissipates, unlike chemicals which often leave white trails,” he said, adding that officials are investigating the cause of the explosion as well as checking the origin of the canister and the place used to store canisters.

Police said the exploded canister was about six years old and had no pressure gauge. It was filled and weighted earlier at a facility in Phattanakarn area.

Chadchart added that besides providing compensation to the deceased and injured, the city will also send psychologists to help the students deal with trauma.

“There has never been an incident of a fire extinguisher exploding in Bangkok, so we must learn from this incident,” he said.

“The city is purchasing over 10,000 extinguishers to be delivered to local communities. They are of a different type from the one that exploded and have lower pressure, so there is no need to panic,” said the governor, adding that the city will increase the intensity of safety inspections of all purchased extinguishers.

Deputy Governor Tavida Kamolvej added that the city will also survey the places used to store and install fire extinguishers at schools and public buildings, and will avoid putting them in direct sunlight which could increase internal pressure.

“This incident also taught us to review the procedures in organising fire drills in schools to ensure student safety, as well as to include lessons on proper care and maintenance of fire extinguishers,” she said.