Three people were killed after a small amount of chlorine leaked Friday at a chemical factory in east Shandong Province, said the local work safety watchdog.

The accident occurred at around 4:00 p.m. at the Shandong Hengtong Chemical Co. in the city of Linyi, according to the provincial work safety bureau.

An initial investigation showed that the gas leak poisoned some workers, but the exact number has not yet been determined.

The cause of the accident is under investigation.