A power outage forced officials to close Philadelphia City Hall and all court operations midday Monday.

The outage occurred just before 1 p.m. when employees were sent home. Power was restored about an hour later, PECO spokesman Greg Smore said.

An underground cable that powers City Hall and other buildings in the area went down and a mechanism for switching over to a backup line failed, Smore said.

"This is just one of the lines that City Hall has to power the building," Smore said. "They had an issue with their internal equipment that would make that switch, so our crews arrived on site and we were able to help make that transfer and restore power about an hour later."

Crews remain in the area working to fix the underground line that went down. City Hall will be open normal hours on Tuesday.

Two separate power outages in August and September also shut off electricity to City Hall, which opened in 1901 and is one of the largest municipal buildings in the world.