Some phone and internet service is back up in Yukon following a major telecommunications failure in the territory and the Inuvik area of the Northwest Territories.

Northwestel says phone service has been restored to most of Whitehorse, and cable internet has been restored to about half the city.

Northwestel said the problem began when its backup generator shut down after power was restored to its central office in Whitehorse following a citywide outage overnight.

Landlines, cellphones and internet services were knocked out in Yukon and the Inuvik area. Cellphone and internet in Iqaluit were also affected.

Yukon Energy workers say last night's power outage in Whitehorse was caused by a tree that was blown down onto a transmission line near the McIntyre substation.

Laurence Jowdry, director of engineering at Yukon Energy, said communications were working fine when crews restored power last night.

"Actually the phones stopped working after the power was back on so we had everybody restored and that's when it seemed the phones stopped working," he said. "But it was very fortunate, because we would have relied probably on our internal mobile system."

Jowdry said the tree is being removed and regular operations on that line should be back to normal by this afternoon.

Emergency 911 phone service, which was also affected, was restored before 10 a.m. PT.