Bangkok: An accident at the headquarters of Thailand’s Siam Commercial Bank, possibly caused by a fire retardant chemical, has killed eight people, the bank said on Monday.

The accident took place late on Sunday as contractors were working on the building’s fire fighting systems.

‘Gas pyrogens intended to extinguish fires opened and kept oxygen out resulting in injuries and death,’ the bank said.

‘Eight people died as a result and seven injured people are in hospital,’ the bank said.

Those killed were contractors and a security guard, police said. ‘They were in the building for maintenance work,’ said Police Colonel Charoen Srisasalak.

In Feb. 2015 a fire broke out at the sprawling SCB complex located in the north of the Thai capital Bangkok, killing one fireman.

All SCB bank branches will open as usual on Monday, the bank said. SCB is Thailand’s oldest commercial bank and Thailand’s third largest lender by assets.