Two main power lines malfunctioned Thursday night and knocked out service to about 70,000 customers across the Annapolis area for at least three hours, BGE officials said.

The utility lost service reported a loss of service to two major lines about 8:55 p.m., and for a couple of hours, officials didn’t know what caused the outages, said Rob Gould, a spokesman.

The company website reported outages as far north as the Herald Harbor area of Anne Arundel County to Highland Beach to the southeast.

Company officials said workers later found the source of the problem: a fallen power line just north of Annapolis. Gould said power should be restored to all customers by early Friday morning.

This story has been updated.