Tens of thousands of hydro customers in downtown Toronto have their power back after a massive outage on Thursday that forced some businesses to close and caused headaches for drivers.

Power was restored just before 8 p.m., nearly eight hours since the outage began.

"Safety is always our top priority. We know this power outage has made today exceptionally difficult for many of you, and we appreciate your patience," David Lebeter, the chief operating officer of Hydro One, said in a statement on Thursday evening.

"We had all available resources helping to restore power as quickly and safely as possible. I want to thank all of those affected by this outage for their patience and Toronto Fire and Toronto Hydro for their collaboration."

Hydro One said a crane in an upright position that was on a barge travelling in the Port Lands' Ship Channel around 12:30 p.m. ran into three high-voltage transmission lines, causing further downstream damage to equipment at its power station near The Esplanade and resulting in power being lost throughout of the downtown core.

Outage

At its peak, an estimated 10,000 customers were left in the dark.

For several hours, the outage knocked out power to parts of the Hospital for Sick Children's campus. It also darkened a portion of the Eaton Centre, forcing the closure of hundreds of stores. The mall, however, reopened at around 3:30 p.m. after power was slowly being restored.

Many large advertising screens at Yonge-Dundas Square also went dark. Traffic lights were down in some downtown intersections, prompting police to remind drivers to treat them as four-way stops. It led to some thoroughfares jamming up.

CTV News Political analyst Scott Reid was driving downtown when the lights went out.

He said navigating the city's streets was a bit "hairy" as several traffic lights are out in the downtown core.

Reid said police officers were directing traffic at some major intersections, but not all.

 Power outage

The outage did not impact subways, but the TTC said there were significant streetcar delays due to traffic lights being out in parts of the downtown core. Meanwhile, Metrolinx said its PRESTO, GO Transit, and UP Express services were all running. It added that Union Station never lost power.

Several people were also trapped in elevators due to the outage. Toronto Fire said crews responded to a number of elevator rescues.

No injuries have been reported at this point in connection to the outage.

"(It was) definitely a unique situation," Hydro One spokesperson Tiziana Baccega Rosa said.

She noted that an investigation is ongoing into the circumstances of how that barge was moving with a crane in an upright position and not adhering to the safety protocols.

Hydro One said crews will continue to work in the coming days to fix the damage caused by the crane.

Outage

City launches investigation

In a statement, the city said that a subcontractor to Southland-Astaldi Joint Venture (SAJV), which is involved in the Ashbridges Bay Treatment Plant outfall project, may have caused the outage.

"The city has launched a full investigation and has requested a full report from SAJV to understand what happened and what needs to be done to ensure this does not happen again," the statement read.

Toronto Mayor John Tory said in a separate statement that the outage caused tremendous disruption in the downtown area and that it should not have happened.

"I want to thank the team from Hydro One who worked with our Toronto Hydro team to restore power to those affected as quickly as possible," Tory said.

The mayor said city staff and all relevant parties will be reviewing the incident to ensure that it will not be repeated.

"I have been clear to city officials that I support them doing everything possible to get to the bottom of this and ensure full and complete accountability," Tory said.