A problem with a transmission line caused 6,900 Central Maine Power customers in Greater Portland to lose their electricity for a little more than two hours early Monday.

Customers lost power in South Portland, Cape Elizabeth and on the Portland islands of Great Diamond and Peaks, said Catharine Hartnett, a CMP spokesperson.

The outage was caused by a failed transmission line, Hartnett said, at a substation near Hinckley Pond on Highland Avenue in South Portland. Linemen did not find any damage to the line, and were able to re-energize it. The outage lasted from 2:11 to 4:33 a.m., Hartnett said.