A hydro outage has hit the core of Toronto’s downtown financial district, affecting some of the city’s largest office towers and leaving thousands of white-collar workers without power.

Buildings affected are located on Wellington, Front, Richmond and King Streets, and include the GO Transit terminal on Front Street and First Canadian Place, which houses the Toronto Stock Exchange, Global Ontario reports. Disruptions to GO Transit service or trading have yet to be confirmed. Some of the buildings have backup emergency power generators to keep some lights on and keep people from being trapped in elevators.

According to Toronto Hydro, as many as 120,000 people could be in the dark as a result of the outage, which began at 1:30 p.m. ET. The outage was apparently caused by a “feeder trip,” or a disruption to the primary “feeder” wire that carries power to the area.

Toronto Hydro believes that power should be restored by approximately 4 p.m. ET.