Three Mississauga firefighters are recovering in hospital Thursday after being injured in a massive explosion caused by a fire at an industrial warehouse, as investigators at the site try to determine what started the blaze.

The firefighters were called to a warehouse fire at 2797 Thamesgate Dr., just north of Toronto Pearson International Airport, shortly before 5 a.m. Wednesday. As they tried to enter the building, an explosion collapsed a wall and briefly trapped them inside.

One of the injured firefighters was admitted to hospital in critical condition, but was later reassessed as having serious-but-non-life-threatening injuries. The other two suffered broken bones, and a fourth firefighter was treated for smoke inhalation at the scene.

The City of Mississauga issued a news release on Thursday afternoon identifying the firefighters who were injured, though the document did not identify which individuals remained in hospital.

The city identified the injured firefighters as:

  • Capt. Brad Hamilton, 38
  • Acting Capt. Al Mills, 47
  • Tim Casarin, 46
  • Daryl Roy, 35

Emergency crews remained on the scene throughout the night Wednesday, and were still dousing hot spots and manoeuvring around possibly contaminated pools of water as of Thursday morning.

Investigators are still trying to figure out what exactly caused the fire and explosion, but they have been told that there was butane lighters, aerosol insect spray cans, pesticides and printer toner being stored in the warehouse.

Mississauga Fire

Police said air quality was a major concern following the Mississauga, Ont., fire due to the potential nature of the substances stored in the building. Air quality tests were conducted throughout the day, but no neighbourhood homes had to be evacuated. (Tony Smyth/CBC)

Deputy fire chief Greg Laing said Wednesday that fire crews had no idea the building contained explosive materials — believing the warehouse to be vacant —  and that it “was a miracle that no one is dead.”

According to Laing, the business had not yet been inspected to determine whether it met with proper building and fire codes.

Mississauga Mayor Hazel McCallion said that that as far as city officials can discern, the import company that using the building, G.E. Forwarders, has not applied to the city for an occupancy permit.

“It is essential for the sake of saving lives that and especially the life of our fire fighters by letting the city know that they are occupying the building and what they're going to do in the building,” McCallion said.

The Ontario Fire Marshal’s office is investigating.    

With files from The Canadian Press