HANGZHOU - A poisonous gas leak at a workshop in Hangzhou, capital of East China's Zhejiang province, on Monday morning killed one person and sent six others into comas.

The authority in Fuyang city under the administration of Hangzhou said the accident happened at 10:40 am. Three of the injured are still in a critical condition.

Firefighters have turned off the gas supply to stop the leak.

The gas has been identified as arsenide cyanide, a lethal byproduct yielded through processing and storing arsenide minerals.

An investigation into the accident is under way, and staff from the Fuyang environmental department have been sent to the site.