12/10/2017 08:34 EST | Updated 12/10/2017 08:40 EST

Poor ventilation at B.C. greenhouse blamed for carbon monoxide poisoning

DELTA, B.C. — A fire chief says poor ventilation at a Delta, B.C., greenhouse is to blame for sending dozens of workers to hospital for carbon monoxide poisoning.

Delta fire battalion chief Neil Shuster says an emergency call came in Saturday afternoon that at least 12 people at Windset Farms were suffering from inhalation of a suspected chemical agent.

He says once on scene, crews determined carbon monoxide was the culprit and at approximately 43 people required treatment on site.

The workers had been inside a greenhouse while a gas-powered pressure washer was running without adequate ventilation.

Representatives from Windset Farms did not immediately respond to requests for comment.

Shuster says about 35 people were sent to hospital but all have since been released.