A “painstaking” investigation into the cause of a massive “wind-driven fire” at an under construction residential building in Mississauga is now underway, the city’s fire chief says.

The three-alarm fire broke out at a four-story under construction building in the Tannery Street and Joymar Drive area of Streetsville shortly after 7 p.m. on Friday.

Mississauga Fire Chief Tim Beckett says that by the time crews arrived on scene the structure was completely engulfed in flames and could not be saved.

He said that crews on scene worked to pump water onto neighbouring properties, including a senior’s residence, to prevent the blaze from spreading.

Beckett said that some of the exterior windows at the senior’s residence were cracked amid the heat but he noted that those inside were “never in danger.”

“By the time the crews got on scene the fire load was so heavy that we couldn’t do much other than protect the exposures and limit the damage to the building involved,” he told reporters at the scene on Saturday morning. “That is the problem that we see with wood frame construction. It is a solid building platform but when it is susceptible to fire during its construction phase, it moves pretty quickly.”

One firefighter injured

At the height of the blaze there were about 60 firefighters on scene, as well as 15 fire trucks. .

Beckett said that one firefighter did sustain a minor hand injury after slipping on some ice but he said that they are expected to make a full recovery.

Meanwhile, he said that crews are continuing to put out hot spots and will likely continue doing so into this evening.

At that point, heavy equipment will likely be brought in to knock down several remaining portions of the structure that Beckett said “could collapse at any point.”

Investigators from the Office of the Ontario Fire Marshall are also on scene and will begin sifting through the rubble once they are given the all-clear.

“We have a lot of rubble that has occurred and it is going to be a painstaking investigation to find the cause of this but I have confidence in the fire marshal and my team,” Beckett said.

Power was shut off to about 1,100 homes during the fire as a precaution but Beckett said that service has been restored to most of those properties.