CENTER TWP — Firefighters early this morning prevented a basement blaze from spreading to the rest of a ranch-style house on Sawmill Lane.

Chief Greg Brewster of the Unionville Volunteer Fire Department said the cause was apparently electrical.

“It looked like an electrical heater,” Brewster said.

He said clothes in the laundry room caught fire.

Brewster said there was only smoke damage to the Nelson residence at 121 Sawmill Lane.

More than 20 firefighters responded to the 1:03 a.m. 911 call about the house being full of smoke.

The Mercer Road and Butler Township Fire District Station 3 volunteer fire departments assisted Unionville.

Crews cleared the scene by 3 a.m.