Plant sirens sounded at Imperial's Sarnia manufacturing site late Wednesday morning.
A Chemical Valley alert was issued for a fire at the plant.
Company spokesperson Kristina Zimmer said there was a small tank fire.
"The tank, which contained a wax-like material, is located in an area of the site that's under demolition," Zimmer told BlackburnNews.com in an email. "There were no injuries, the cause is under investigation, and air monitoring is being conducted as a precaution.
Zimmer said there was visible smoke coming from the tank but Imperial emergency responders were able to extinguish the fire.