Nearly 12 hours after a fire broke out in a Mississauga apartment building, power has partially been restored and residents are slowly being allowed to return.

The fire began around 1 a.m. Friday on Mississauga Valley Boulevard, near Hurontario Street and Highway 403.

It started in the third-floor electrical room and spread to the fourth floor, Mississauga Fire officials said.

The building was evacuated and about 100 residents were sheltered on transit buses. Two people were taken to the hospital for smoke inhalation.

Around 7:30 a.m., emergency crews began to shuttle residents to the Mississauga Valley Community Centre.

Residents on the fifth floor and above were allowed to return in the hours after 9 a.m. But those on the fourth floor and below will have to wait until repairs have been completed.

Power was mostly restored by 12:20 p.m., officials said.

Peel police said they would be kept out until the electrical system has been inspected and declared safe by a building electrical engineer.