Thousands of Butler County residents were without power Sunday afternoon as storms ripped through the region, but most have now had electric service restored, a West Penn Power spokesman said this morning.

About 3,000 customers were affected Sunday afternoon and evening, said company spokesman Todd Meyers.

The largest group of outages started at about 3:30 p.m., when about 1,500 customers in the Portersville area lost power after an unexplained problem at a substation.

Meyers said the company couldn’t identify the problem, but power was restored after about 20 minutes when workers reset equipment.

The remaining outages were scattered across the county and were caused by strong winds pushing trees onto power lines, Meyers said.

West Penn worked overnight to restore service to most of the affected customers.

The remainder — 123 in Allegheny and Center townships — were to be back in service by late morning.