Five workers died Tuesday after they fell into brine vat at a pickle factory in Chongming county, the Shanghai Administration of Work Safety said.

Nine of the factory's workers fell into the vat around 2:55 pm.  Investigators suspect that the workers died from hydrogen sulfide poisoning.

The accident happened after one of the workers fell while cleaning the vat. The other eight workers then fell inside while trying to rescue him.

The injured workers were sent to Chongming Central Hospital. Two remained in a coma Tuesday.

The case remained under investigation Tuesday.