Dozens of students at the University of Denver became ill over the weekend, and seven students remain hospitalized today.

The Denver Health Department is investigating the mass illness but has not yet come up with a cause, said David Brendsel, a university spokesman.

Symptoms include vomiting, diarrhea, stomach cramps, nausea, dizziness and dehydration.

A total of 42 students reported being ill since Sunday, Brendsel said.

At least 13 students were treated at the university's health and counseling center, and at least 24 were taken to Porter Adventist Hospital, where seven remain today, Brendsel said.

Investigators haven't determined whether the illness is viral or bacterial, Brendsel said.

"We are still working with Denver Health to determine the cause of the illness," he said.

Most of the students reside in Centennial Halls on campus. The complex, which houses 625 students, includes a kitchen and dining areas.

Health and school officials have "found no safety issues at Centennial Halls," and the kitchen and dining area have remained open.

No students have reported illness today, Brendsel said, and recovery time for most students was 24 to 36 hours.

Health officials and university officials have been reminding students to consistently wash their hands to cut down on the chance of illness, Brendsel said.