Hydro One supply coming into Sarnia was cut late Thursday morning causing a widespread power outage.
The entire city and parts of Lambton County were impacted, initially affecting 33,000 of Bluewater Power's 36,000 customers, the most since the blackout of August 2003.
Power was restored before noon to Petrolia, Enniskillen, Brooke-Alvinston and Watford, but much of the city remained out until nearly 2 p.m.
Bluewater Power CEO Janice McMichael-Dennis said their main Modeland station that feeds the city from Hydro One completely lost power.
"What I have been told is that there was a third party contractor employed by Hydro One who dug into an underground major cable when they were doing work on the Hydro One system somewhere outside the city of Sarnia," said McMichael-Dennis. "That resulted in a system fault or system damage that brought down the entire Hydro One station."
Hydro One spokesperson Alicia Sayers confirmed a contractor's equipment made contact with a high voltage transmission line at about 11:15 a.m. "Our crews worked quickly and safely to separate the equipment from the line and there are no injuries reported at this time," said Sayers.
McMichael-Dennis said they adjusted their own system to restore as many customers as possible, until Hydro One was able to fully restore service at 1:47 p.m.
During the outage drivers in the city were told to treat intersections without working traffic signals, as four way stops.
