Regina Fire and Protective Services completed their investigation later that evening.
An initial explosion was caused by sparks from a grinder that ignited fumes in a vehicle gas tank, according to Regina fire.
Crews responded to reports of the explosion and detached garage fire in 4400 block of 7 Ave. at about 8:45 p.m., where they found a critically injured man laying in the alley.
According to officials, a second person was able to escape uninjured.
While firefighters were putting out the fire, an explosion occurred caused by a nitrous oxide pressure vessel. Shrapnel from the vessel hit two firefighters and damaged a fire truck.
The firefighters were not injured, but the man died from his injuries on Saturday morning.
Regina Fire & Protective Services is reminding residents of the danger of using spark or flame producing equipment in confined areas with the presence of flammable or combustible liquids and vapours.