A number of Yampa Valley residents and businesses lost their power for more than an hour Tuesday afternoon.
Jim Chappell, spokesman for Yampa Valley Electric Association, said crews were investigating what triggered the power outage, which happened about 4:30 p.m.
"We're not really sure what happened," he said.
A variety of factors could have caused the outage, which affected at least 1,000 people north of Steamboat Springs and west of Steamboat to Milner.
Chappell suggested a plane, downed tree or lightning may have touched a power line and produced the outage. A plane that flew too close to a power line caused a similarly sized outage a few years ago, he said.
"It's got to be something fairly serious," he said.
Crews used a helicopter in their investigation of how and where the outage occurred. The incident occurred at a bad time, because many crews were heading home for the night. Employees were called back in, and Chappell said crews would work until power was restored to all residents.