The department says it has warned Reliance Ltd. in suburban Pointe-Claire to remove waste contaminated with polychlorinated biphenyls from its property.
Several inspections have been carried out by the Environment Department, which says materials that could be hazardous to humans and the environment are present.
The government says it only learned of the materials after a spill of between 800 to 1,200 litres of oil and oily water containing PCBs on the site on March 26, and that the company was not authorized to store such material there.
On Aug. 13, Reliance was ordered to secure the site, inventory the material and prepare for its removal.
The government said Reliance has taken some measures to correct the situation but not enough and does not rule out further action.
A private security firm has also been hired by the Environment Department to watch the property.