An old tree branch in south Mandan went out with quite a bang Tuesday night.

By the time the smoke cleared - and there was some smoke - the branch could claim responsibility for dousing the stop lights on Main Street and killing power to about a quarter of the city.

The branch got tangled in a power line on Sixth Avenue Southeast at about 6:30 p.m., which threw a breaker at the nearby substation and knocked out power to roughly 1,100 Montana-Dakota Utilities customers.

A crew came in to fix things and had the power back up by 8:15. But then the breaker failed.

"It started smoking," MDU spokesman Mark Hanson said. "If your breaker isn't working, that's not good. So they took down the whole substation by Dan's (Supermarket) to replace that breaker."

The BN Substation, as it's known, was "de-energized" from 8:26 to 8:42. That killed power to 4,100 homes - about a fourth of Mandan.

The majority of the homes were south of Main Street, which also had street lights and stop lights go dark.

A Mandan Police Department dispatcher said she hadn't taken any accident calls on Main Tuesday evening.

The power was back up at 8:42, and MDU employees will check the failed breaker today to determine what went wrong, Hanson said.

(Reach reporter Tony Spilde at 250-8260 or tony.spilde@;bismarcktribune.com.)