There is no word yet on when hundreds of Torontonians will return to their homes after power was knocked out at two apartment buildings in separate incidents on Thursday.

The first incident happened at a nine-storey condominium apartment building located at 3650 Kingston Road.

Firefighters were called to the building at 2:30 a.m. Thursday, after residents reported hearing blasts that woke them out of their sleep.

City of Toronto spokesperson Patricia Trott told that it has since been confirmed that two explosions rocked the building on Thursday morning, the causes of which have yet to be determined.

"Fire responded to a call at about 2:30 a.m. (Thursday) for signs of smoke, and they determined that there had been an explosion in the building's electrical room and that there was also an explosion outside in a hydro vault," Trott told in a phone interview.

Trott said it is not yet clear which explosion occurred first, though Toronto Hydro said Thursday that an outdoor transformer had been damaged by the incident that took place inside the building.

Several investigations and repairs have to take place before residents can return home, Trott said, though it is not yet clear when that will be.

"There were structural engineers who were brought in yesterday by the property management company and the building is structurally sound," she said.

"It's just that there is no power and no safety systems in place, so that's why it's not safe for people to be living in the building."

Figures from building management suggest that some 500 adults and 150 children live in the Kingston Road building, Trott said.

Residents have been offered temporary shelter by the city at a nearby community centre.

The second incident occurred early Thursday afternoon at 2369 Lake Shore Blvd., in the third-floor electrical room of a four-storey, 92-unit apartment building.

City of Toronto spokesperson Kevin Sack told on Friday morning that residents were evacuated because the power was out.

"The building has been evacuated because it's not safe," he said. "Without electricity, there's no sprinkler or fire alarm system."

Residents have been offered temporary shelter at a community centre nearby, Sack said.

About 30 people made use of the emergency shelter on Thursday evening, he said.

There will be no estimate of when power will be restored until the Office of the Fire Marshal completes its investigation, Sack said.

While authorities were inspecting the damage to the building, they came across another problem: The presence of a presumed marijuana grow-op in three of the units within the building that drug squad officers were investigating on Friday.

With a report from CTV Toronto