Power has been fully restored at Toronto City Hall three days after an electrical fire plunged the building into darkness and forced an evacuation.

The Queen St. West facility lost power on Thursday, following a fire in a hydro vault located in the basement.

The early afternoon blaze forced 1,500 staff from the building, which has remained close for the past three days. Two people working in the electrical room also suffered minor smoke inhalation.

Crews were working over the weekend to get the building’s electrical system back online. In a news release posted on the city’s website, officials said temporary generators are providing power to the building as permanent repairs to the electrical system are carried out over the next several weeks.

Officials said they are also monitoring air quality in the building to watch for carbon monoxide levels while the generators are running.

Toronto Fire has also tested the fire and life safety system in the building.

City hall staff are being told to report for their scheduled shifts on Monday. The on-site day care, café and public library are expected to resume normal operations.

An investigation into the cause of the fire is underway.