Emergency crews have now contained a massive blaze at a residential building under construction in the Streetsville neighbourhood of Mississauga.

Peel Regional Police say they were called to the Tannery Street and Joymar Drive area of Streetsville at 7:05 p.m. for a report of a massive fire.

They say it appears to have originated in a building under construction.

Witnesses at the scene posted videos to social media where explosions could be heard.

After more than two hours of fighting the flames, firefighters said they had no reports of any injuries and the fire was largely contained by 9:30 p.m.

Residents at the scene told CP24 the epicenter of the fire is a building under construction. It is next door to a seniors’ home, the Credit River Retirement Residence.

Firefighters could be seen on the roof of the seniors’ home.

A man who identified himself as Paul said he was waiting at a police staging area for news about his mother-in-law who lives in the seniors home.

“They’ve moved all the residents to the north end of the building, on the east side, because the flames are moving towards the south. So they’re trying to keep everyone at this end, for smoke and everything else and to keep them calm.”

He said he has so far been unable to get in touch with her.

Police said the seniors were "sheltering in place" and officers were ready to evacuate them if necessary.

Const. Lori Murphy says a number of homes were evacuated near the fire scene but the seniors’ home was never evacuated.

A pair of residents told CP24 they heard an explosion while sitting in an elevator in their condo building more than one kilometre from the scene.

By 8:20 p.m., police said about 1,100 homes in the vicinity of the fire had lost power. The outage was reduced to 225 households by 10:15 p.m.

Robert Ricard and his wife were forced to leave their home about 10 minutes after the blaze erupted.

“I was outside watching it. You could hear the gas tanks going off. I stood out there for about 10 minutes and then the police came and told us to leave.”

He and his wife stayed at an emergency staging area in a transit bus for a while before their daughter came and drove them to a hotel.

Police urged motorists to stay off Queen Street, south to Eglinton Avenue West for the duration of the incident.