DULLES, Va. (AP) _ An electrical problem at an America Online technical center shut down the nation's largest computer online service for more than 2 1/2 hours during peak usage time Monday night.

AOL's entire system crashed beginning at 9:15 p.m. EST because of a problem at its technical center in northern Virginia.

``We were able to resume operations by 11:45,'' said AOL spokeswoman Wendy Goldberg. ``We still don't know what caused the electrical problem.''

E-mail service for AOL's 11 million members was not restored until around 2:30 a.m., she said.

The malfunction follows AOL's announcement earlier this month that it plans to increase its monthly flat rate for unlimited service from $19.95 to $21.95.

AOL said it is raising rates because members are staying online longer. The amount of time members spend online has increased from an average of 14 minutes per day to 50 minutes per day, Ms. Goldberg said.