A forest fire burning under the main transmission line between the Snare hydro facility and Yellowknife caused power outages in the city Wednesday afternoon.
The Northwest Territories Power Corporation says crews can't get to the damaged line because of the fire, so the power could go out again in Yellowknife and nearby Dettah.
Meanwhile, lightning has damaged some of the city's backup generators at the Jackfish Lake diesel plant. Crews are working to repair the generators, but Yellowknifers are being asked to conserve energy.
The power corporation says if power from the Snare hydro system is lost again before generator repairs are completed, electricity demand in the city could approach the Jackfish plant's capacity.
A forest fire is suspected to have damaged a different spot on the Snare line to Behchoko Tuesday, causing power outages in North Slave communities. Behchoko, a community about 100 kilometres northwest of Yellowknife, is still being powered by its diesel plant.
Earlier Wednesday, Pam Coulter, spokeswoman for the Northwest Territories Power Corporation, said crews couldn't get to that area because of heavy smoke, but it's believed fire is to blame for the damage.
"From the air, it looks like a couple of the towers are burnt at the bottom, but there's a lot of heavy smoke in the area," she said.
"And until we get clearance from [the Department of Environment and Natural Resources] we can't actually get on the ground to investigate, access and then repair it."
Coulter said people in Behchoko should conserve as much power as possible, because diesel is an expensive fuel to burn.
She said this fire season is one of the worst the power company has ever experienced.