MISSOULA, Mont. -

**UPDATE***

Northwestern Energy officials say power has been fully restored to approximately 4,000 people affected by a power outage in Missoula.

Officials say the outage lasted for approximately 2 hours, and ended around 9:20 p.m.

A problem at a substation on Miller Creek Road reportedly caused the outage. We're told heat might have been a contributing factor.

***

A blown substation has knocked out power to thousands of people in Missoula.

Northwestern Energy officials said 3,000 to 6,000 people on the south side of town are without electricity.

Crews are currently working on Substation Five in an attempt to restore power, but Northwestern officials say they have no estimation for when it will be restored, and Missoula County dispatchers say it could take several hours at least.

County officials ask residents to treat lighted intersections that are down like four-way stops.

NBC Montana will update this article with information as soon as it becomes available.