The failure of a digital card on the fourth wheel caused a massive electrical blackout Wednesday afternoon, says Yukon Energy spokeswoman Janet Patterson.

She emphasized the latest problem with the power was not with the governor on the fourth wheel which shut down the system in late October for several hours. That failure also caused Yukon Energy to take the largest turbine in the territory off-line for several days.

The card, she explained, provides information to the governor.

Power went off at 3:28 p.m., was back on in some areas like downtown Whitehorse shortly before 4 p.m., and was fully restored across the grid by 4:30.

Staff at the Canada Games Centre had to ask users to leave, and shut down the facility.

With last month's problems with the number four generator, and the number three turbine, Yukon Energy was forced to bring in an expert from Wisconsin to assist with the troubleshooting.

The publicly-owned power corporation was also forced to use diesel generators while the hydro units were off-line. That resulted in the cancellation of the sale of secondary power to the company's 22 commercial customers.

The surplus secondary power is sold at bargain prices, and allows businesses to use the cheaper and electricity for heat rather than burning heating fuel.

Sales of secondary power have been restored.

The Whitehorse General Hospital is a user of secondary power. Administration estimate it was costing an additional $500 to $600 a day to run the hospital without the benefit of secondary power sales.