The incident happened at about 7 a.m. at a warehouse specializing in welding in the Jonquière district.
Initial reports suggest an accumulation of gas from work being done inside the warehouse led to the explosion.
A man, in his 40s, was hit by a metal plate thrown by the blast. He had serious injuries to his legs, but his life is not in danger.
The workplace health and safety board will investigate.Suggest a correction