Problems with three PEPCO feeders in Rockville kept Montgomery County government’s computer system down for most of Thursday, officials said. While electricity remained on and no offices closed, the power failure slowed routine business, said spokesman Patrick Lacefield.

The problem, which started at about 11 a.m., also took out county e-mail, voice mail and its 311 call center. The back-up system was also rendered inoperable. Lacefield said the 911 emergency system, which operates on a different server, was not affected.

He said the data system should be operational by the opening of business Friday.