Technology designed to save soldiers on the battlefield helped save lives and property Tuesday during a fire at an Etobicoke, Ont. apartment building.

What started as a fire in a car parked beneath the building turned into a blaze that threatened the entire structure on Lakeshore Blvd. west of Parklawn.

It happened just after 2 p.m. and when more than 60 firefighters arrived at the scene the blaze had spread to four apartments.

"It got inside the walls and extended up two floors," Platoon Chief Mike McKoy said, adding that the blaze required some "aggressive firefighting."

At first it was feared that residents were trapped inside the burning building.

But firefighters on the scene had a high-tech tool that was originally developed for military use. A thermal imaging camera allowed firefighters to see where the fire was spreading behind walls.

More importantly, the camera let rescuers see where people were inside the burning building.

"Basically, you're looking at things by the heat that they generate," firefighter Ray Brock said.

"It will show you where hot spots are in a wall, wherever it's warm, so that way we're able to locate the fire when we can't see it."

Thermal imaging technology was developed by the military about 50 years ago. Since that time the technology has become small and compact enough to be used every day by firefighters.

Toronto firefighters said that if it wasn't for the camera, the building's more than 40 apartments would likely have been destroyed, with a very real chance that lives would also have been lost.

With a report from CTV's John Lancaster