Eight people died at the headquarters of one of Thailand's largest banks when workers accidentally triggered the release of fire extinguishing chemicals during an upgrade of the building's safety system, officials said Monday.
Seven other people were injured in the accident, which occurred Sunday night in the basement of the Siam Commercial Bank's headquarters in Bangkok.
The bank said in a statement that an initial investigation found that the accident was caused by "negligence on the part of our contractors hired to improve fire protection in the building."
Workers were upgrading a fire extinguishing system in a document archive room in the bank's basement when the accident occurred, causing the release of Pyrogen aerosol, officials said. They did not elaborate.
Police were investigating the accident and the bank said it would release more information after a meeting of its board members Monday.
Pyrogen is a chemical fire retardant normally intended to deprive fire of oxygen and is typically used in places where extinguishing a fire with water would damage documents or equipment.
Pyrogen's website says the dense aerosol is "most effective in unoccupied areas such as data rooms, machinery and engine spaces" and other storage areas. It says people should avoid exposure to Pyrogen and any "accidental exposure to the aerosol should be limited to five minutes."
The bank identified those who died as a security guard and seven contractors.
Bangkok's Erawan medical emergency centre said five people died at the site of the accident and three died later at a hospital. It said the apparent cause of death was suffocation from insufficient oxygen, but that the official cause would not be known until autopsies are performed.
Seven other people suffered suffocation-related injuries, including four who were in serious condition, Erawan said.