An explosion at a chemical production plant in Bécancour forced the evacuation of several companies in the area, although employees working for the plant where the explosion happened were told to stay put.

The Surete du Quebec set up a wide perimeter around the Olin Chlor Alcali plant, located at 675 Alphonse Deshaies Blvd. in the industrial park after the 11:30 a.m. blast.

Bécancour fire department didn't enter the Olin plant gates after explosion, explaining that special teams would handle the issue.

Witnesses reported seeing a large yellow cloud, which would likely be chlorine gas, coming from the factory.

Reporters on site right after the explosion said the fumes were overpowering.

Melanie Dumaresq of the SQ said a deliveryman in the area at the time of the explosion was taken to hospital after being overcome by gas, but is expected to make full recovery.

The company confirmed that there was a chlorine release earlier, but it has now been stopped. The Olin plant says the release does not pose a threat to those in the area or the environment.

Environmental officials will survey the area before giving people permission to return.

Olin Chlor Alcali produces several products such as hydrochloric acid, chlorine, sodium hydroxide, all of which are made by running an electrical current through salt water and collecting the resulting gases.