Yukon Energy workers are trying to track down the cause of a power failure that left most residents of the territory in the dark on Sunday.

Thousands of people in Yukon were without power for more than nine hours Sunday, after a failure at the Aishihik power dam northwest of Whitehorse. Electrical service resumed after 10 p.m., though officials are asking the territory's residents to conserve power.

The power failure affected about 90 per cent of the Yukon, including residents in Haines Junction, Carmacks, Carcross, Teslin and Whitehorse.

Janet Patterson, a supervisor of communications with Yukon Energy, says a problem with one of the generators at the Aisihik power station caused a cascading failure in the power grid, overloading a second generator at the dam and then the Whitehorse power station.

The situation was becoming dangerous, with temperatures in many locations reaching below -30 C, when officials said they were close to having to institute rotating blackouts. The situation stabilized enough, however, that the measure wasn't necessary.

Emergency Measures officials monitored the situation throughout the day. At an early evening meeting with Yukon Energy officials, they decided the situation was in hand and warranted no action on their part.

Hydro officials are asking Yukon residents to still conserve power to reduce the load on the system, until the source of the problem can be tracked down.

"I would encourage people, if they can try to conserve as much electricity as they can over the breakfast period," says Patterson. "Keep your showers short, don't run the dishwasher, save that for later. [Those] sorts of things."

Patterson says if there is too much demand for power, there would have to be rotating power outages. But she says the energy corporation hopes that can be avoided.