BOULDER, Colo. -- Enrollment at the University of Colorado is up -- and so is the number of run-ins between police and students.

Officers say 351 people were ticketed for underage possession or consumption of alcohol in the University Hill area, across from the Boulder campus, during the first three weekends. That's a 53 percent jump from last year.

Police also ticketed 59 people for nuisance parties, confiscated 62 beer kegs or taps and arrested 19 people over those three weekends. All are substantial increases over the year before.

"We certainly were more active this set of back-to-school weekends," police spokeswoman Sarah Huntley said.

Injuries to three officers as they wrestled with suspects are particularly troubling, Huntley said, because of the increased level of noncompliance police have seen. One officer hurt her ankle and two injured their knees.

Not all the scofflaws are students, but police believe the influx of people due to the university's largest-ever freshman class is largely to blame.

University officials say a record 5,833 freshmen are enrolled on the Boulder campus this fall. Overall enrollment is 29,709, a 2.5 percent increase over last year.

Police said 65 people were ejected from the CU football game against West Virginia, including 43 for alcohol-related violations.

CU police Cmdr. Brad Wiesley said many of the other ejections were related to fighting.

The ejections were nearly triple the number from CU's first home game this season. There were 30 ejections at last season's night game against Florida State University.

Some students attribute the increase in tickets to more police on patrol.

"I think the police have increased up here, and that may be why there are more tickets," said Gordon Graham, a CU sophomore who lives near campus. "But at the parties I've been at, and at other places, it doesn't seem that crazy at all."

University officials, though, think the crowds are rowdier.

"I think it's really clear to everybody we've got an issue this year," CU spokesman Bronson Hilliard said.

So far this year, Hilliard said, 662 students have been referred to the university's Office of Judicial Affairs for alcohol or drug violations, up about 10 percent from the same period a year ago.

Hilliard said 70 percent to 80 percent of the cases typically involve freshmen. University officials are working to send the message that the school's code of conduct applies to everyone, on or off campus.

University police Commander Brad Wiesley said officers have seen more activity on campus this year, too. CU officers have issued 187 tickets for violations ranging from drugs and alcohol to urinating in public. Last year, the total was 132.

Wiesley said officers have begun more regular patrols of problem areas, which has likely resulted in more tickets being issued.