More than 300 Central Maine Power customers, many of them businesses near the Maine Mall, lost power Tuesday afternoon, but by late Tuesday night CMP had restored power to several of them, including the Portland Press Herald publishing plant and offices on Gannett Drive.

CMP spokeswoman Catharine Hartnett said power would be restored gradually. Hartnett initially said crews hoped to have power restored to all affected customers by 8 p.m., but there were still 280 outages in South Portland shortly after midnight, according to CMP’s outage reporting site.

Most of the outages affected customers on Cummings Road, Gannett Drive, Sable Oaks Drive, Southborough Drive, John Roberts Road, Maine Mall Road and Running Hill Road.

A CMP crew was conducting routine maintenance on a utility substation around 2:30 p.m. and was beginning to bring power back on when the outage occurred, Hartnett said.

Around the same time as the outage, crews detected another glitch in the system, a damaged underground power line near Idexx Laboratories on Spring Street in Westbrook. Hartnett said crews are investigating whether the maintenance work and defective power line contributed to the outages.