Unalaska made it through a stormy weekend with the lights on, only to lose power Monday morning after a mechanical failure at the powerhouse. 

The outage began around 10:30 a.m. and lasted about 10 minutes. Public utilities director Dan Winters says it's the first unplanned, island-wide the city's had in three years.

"We were swapping engines at the powerhouse, taking down one of our big ones, and ... then everything went black," he said Monday night. "There was a bug in there somewhere."

He says the problem might have been with a voltage regulator on one engine that was coming online at the time of the outage.

But he says it's not related to the installation of the fourth engine at the powerhouse. That tripped a blackout in the Valley neighborhood in September, and prompted a full-scale planned outage last month.