BOULDER, Colo. -- Boulder police are looking for leads in the sexual assault of a female University of Colorado student.

The 18-year-old victim said that a man, possibly between 20 and 30 years old, approached her in a campus parking lot Friday night and assaulted her on the lawn between Farrand and Aden residence halls.

Police Lt. Timothy McGraw said that the attacker was a stranger and will be more difficult to find.

"The fact that this is was a stranger is a little disconcerting," McGraw said. "It doesn't give us an immediate focus."

The man is described as about 6-foot-3, about 250 pounds, with short brown hair styled in a buzz cut. He was wearing a dark T-shirt and baggy pants.