BOULDER — The University of Colorado sent out an emergency text-message alert to students this week for the second time in three days.

CU alerted students Wednesday morning to a 41/2-hour power outage from 2:45 a.m. to 7:30 a.m. in several residence halls, classrooms and administrative buildings.

Roughly 3,967 students in 15 halls were affected by the outage, which was caused by an electrical cable failure. Some were late for classes.

"They had to shower in the dark and get themselves ready with no power available," said Deb Coffin, assistant vice chancellor for student affairs and executive director of campus housing.

CU-Boulder's new text-messaging system, called RAVE, was used to alert some 6,000 subscribers.

It was used for the first time Monday when a man with a history of mental illness stabbed a student on campus.

John Morris, director of Facilities Operations, said the outage was caused by an electric cable failure.

Affected residence halls included Baker, Libby, Farrand, Brackett, Crosman, Cockerell, Reed, Hallett, Willard, Cheyenne Arapaho, Andrews, Buckingham, Smith and the Kittredge West Halls. Farrand, Libby and Kittredge Commons dining operations also were impacted.

Other buildings which lost power were Regent Administrative Center, 914 Broadway and 924 Broadway, Wolf Law Building, Fine Arts, Environmental Design, Coors Events/Conference Center, Ketchum, Imig Music Building, Fiske, Planetarium and the Sommers-Bausch Observatory.