As of noon, electricity had been restored to all customers except for those along Hansen Avenue, said West Penn Power area manager Rob Lombardo.
However, the cause of an outage this morning that left more than 4,000 people without power this morning still has not been found.
Lombardo said something caused the Hansen Avenue substation to go out shortly after 8:30 a.m., and the crews are investigating the cause.
Most of the affected customers were in Butler and Butler Township, with others in Penn, Center and Jefferson townships and East Butler.
Lombardo said that the company generally works to restore power first before looking for an exact cause of an outage.