BOULDER, Colo. -- City police will determine whether charges should be filed in the investigation of a student's accusation she was gang-raped at a party attended by some of the University of Colorado's football players and recruits.

Though campus police have taken the lead, city police chief Mark Beckner said, "We haven't given up total control of the case."

"Certainly if there was a question of whether charges should be filed and we thought they should and they thought they shouldn't, we would take control," Beckner said Sunday.

The investigation however, may be slowed because potential witnesses have left Boulder for the holidays.

Lt. Tim McGraw of the CU campus police said many of the people involved in the case are students, some of whom have left town for the holiday break.

"It certainly will have an impact. Some of the people we'd like to talk to as well as others who they have mentioned, some of those people may be gone," he said Tuesday.

McGraw said it will likely take dozens of interviews before investigators make a determination about charges.

"Frankly, we think it's going to take some time to try to sort everything out and figure out what happened," he said, adding that a decision about charges could be weeks away.

A Colorado student, whose name has been withheld, reported to campus police that she was sexually assaulted by several people at an off-campus party for football recruits on Dec. 7.

Colorado coach Gary Barnett said Sunday the investigation was out of his control.

"We're completely divorced from it," he said. "Once the process is over, we will do the appropriate thing."

Barnett and linebacker Sean Tufts said the allegation hasn't been a distraction as No. 3 Colorado prepares to play No. 2 Oregon in the Fiesta Bowl, on New Year's Day in Tempe, Ariz.

"I don't think it's a big distraction right now," Tufts said. "I would be disappointed if it involves any of my teammates, because they would have done something to hurt this team. This would be the worst possible time."

The National Coalition Against Violent Student Athletes questioned whether campus police were competent to investigate a rape case that might involve the nation's No. 3-ranked football team.

Beckner said campus police took the lead in the case, although the incident occurred off-campus, because the alleged victim reported it to them.

McGraw, who is leading the investigation for the campus police, told Boulder's The Daily Camera he was offended by the suggestion his staff would give athletes deferential treatment.

"We're not under any outside influences," he said Saturday. "Whether or not a person is a member of an athletic team or sorority or any other organization is immaterial."

McGraw said CU police have arrested CU athletes in the past.

"It's discouraging for someone to question our integrity without any foundation," McGraw said.