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

DELTA, B.C. – Poor ventilation at a Delta, B.C., greenhouse is to blame for sending dozens of workers to hospital for carbon monoxide exposure, a fire chief said.

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

Three fire crews and a hazmat crew were dispatched along with police and BC Ambulance Services.

Once on scene, Shuster said crews determined there was high levels of carbon monoxide in the building.

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, he said.

"I believe they were working at the time and it was maintenance, regular maintenance I guess they were doing at the time," he said

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

WorkSafeBC is investigating the incident.

Carbon monoxide is a colourless, odourless gas that's produced whenever fuel is burned.

It can cause health problems — and eventually death — because breathing it reduces the body's ability to carry oxygen in the blood.

BC Emergency Health Services tweeted that 13 ambulances responded to "a major incident" with 10 in serious to critical condition and 32 others in stable condition.

Shuster said about 35 people were sent to various hospitals in the region but all have since been released.

— This story was updated at 11:15 a.m. Sunday, Dec. 10, 2017 with new information.