29 other people were injured by the explosion, mostly sustaining minor injuries. (File)
A high-school student was killed and dozens were injured after a fire extinguisher exploded during a safety drill at a Bangkok school on Friday, police said.
Khumthong Premmanee, 18, died when the extinguisher exploded during an outdoor fire drill at Bangkok's prestigious Rajavinit Mathayom school, police commissioner Thiti Saengsawang told CNN.
Fire station officers were showing the students how to use an extinguisher, with a cluster of the red cylinders displayed behind them in the sun.
"While it was about to be used for demonstration purposes, the CO2 fire extinguisher located behind the trainers exploded," Mr Saengsawang said.
A loud bang was heard and Khumthong was flung almost 30 feet away. The carbon dioxide canister exploded mid-demonstration and sent metal scraps into the 18-year-old's chest. The teen's body had been disfigured when the shockwave and shrapnel hit his torso.
"The explosion hit a student sitting in front of a shrine, propelling his body approximately nine to 10 metres away. He died instantly. The deceased student was not involved in the demonstration but was seated away from the demo area," the official added.
29 other people were injured by the explosion, mostly sustaining minor injuries, reported CNN. The injured were carried off on stretchers and the area was sealed.
Forensics officers said the fire extinguisher had been re-used without a safety valve.
It was refilled with gas and had been left exposed to the sun for a long period, causing pressure to build-up until it finally exploded, they said.
Police have been gathering evidence and CCTV footage from the school. Premmanee will undergo a post-mortem examination, officers said.
Three trainers have been charged with negligence resulting in another person's death.
Education Minister Treenuch Thienthong said it was the first time in six years that the school had held a fire drill, and that it was coordinated by Bangkok's fire department.
She said the department hadn't experienced such an accident before during the many drills it has conducted at schools.