The death of a University of St. Thomas student who went missing in early April has been ruled accidental and was caused by "fresh water drowning," St. Paul police said Wednesday.

The department's investigation into the disappearance and death of Dan Zamlen, a freshman from Eveleth, is now closed, said police spokesman Sgt. Paul Schnell.

While the Ramsey County medical examiner's office has ruled on the cause of death, police were withholding autopsy details -- including Zamlen's blood-alcohol content -- saying the information was non-public under the Minnesota Data Practices Act.

Zamlen, who would have turned 19 on April 9, disappeared after leaving a St. Paul party early April 5, and was last heard crying for help while talking to a friend by cell phone as he walked down St. Clair Avenue toward Mississippi River Boulevard. According to reports, Zamlen, who had Type I diabetes, had been drinking at the party.

Friends and neighbors from the Iron Range joined an estimated 1,200 students in scouring the Mississippi River bluffs in search of Zamlen, and they had planned to do another weekend search when his body was recovered from the Mississippi River near the Ford Motor Co. plant on May 1.

Asked how Zamlen got into the river, Schnell said Wednesday: "We don't know, and we may never know."

Days after Zamlen's body was recovered, police said the medical examiner's ruling depended in part on the outcome of toxicology tests. Schnell said autopsy data is public when a person who is believed to be drunk is involved in a fatal crash, but not in cases such as Zamlen's. The family would have to approve its release, he said.

The family asked not to be contacted by reporters.