The doors of Toronto City Hall remain closed for repairs after an electrical fire in the building's basement sent thick, black smoke billowing in to the air.

Crews are working to install generators to provide temporary power for the building, and repairs to the hydro vault that was damaged as a result of the fire are expected to begin over the next few days. The power is being restored in stages, to minimize the risk of causing further damage.

"City hall employees have been deployed, where possible, and others have been sent home for the day. Essential security and maintenance personnel will remain at City Hall," a spokesperson for the city said in a statement late Friday morning.

The child care centre located in City Hall is also closed but is expected to reopen Monday. Parents have been asked to make alternate arrangements for their children.

Other municipal offices and facilities across the city are open.

In the meantime, many city employees are working at alternative sites for the day, deputy city manager John Livey told reporters.

The only department that had to close and could not be moved was the permit parking office, he said. Drivers can still obtain permits online.

All City Hall offices should re-open on Monday, Livey said.

The electrical fire resulted in the evacuation of as many as 2,000 people. Two employees working in the electrical room were treated for minor smoke inhalation.

Toronto Hydro said Friday that the cause of the fire remains unknown, but an investigation is ongoing.

Air quality tests suggest the building’s air is safe, Livey said.