EUGENE, Ore. — A series of explosions hit an underground utility system Monday at the University of Oregon, plunging several student dormitories and other buildings into darkness as crews scrambled to restore power.

Nobody was hurt, but about 3,000 students living on campus had no power in their rooms, university officials said. Campus police stepped up patrols, and the university gave away flashlights. Officials planned to bring in generators, but the task wasn’t complete by evening.

University officials said electrical equipment overheated, causing circuits to ignite and melt.

The blasts were audible above the ground and from several hundred feet away. A video clip from the campus showed puffs of smoke coming from a manhole cover, and university officials said smoke also was visible inside the university health building, which was evacuated and closed for the rest of the day. A slight smell of burning rubber lingered outside for hours.

It could take days to permanently repair electrical circuits, university spokeswoman Julie Brown said.

Without electricity to power a television or charge a laptop, students were given additional entertainment options Monday, including a watch party for the college football championship game.

In a dormitory near the blast, pitch-black stairwells became obstacles for students trying to get to class, said Camila Rowland, a freshman majoring in psychology.

“We’re using flashlights now,” she said. Some cafeterias were closed, Rowland added, so those with power were unusually packed with students. And officials told residents to try to limit their use of bathroom facilities, she said.