CHICAGO (CBS) — A death investigation was underway Friday at the University of Illinois at Chicago campus, after a woman fell from an outdoor stairwell.

UIC police were investigating after a 20-year-old woman fell off the second-floor stairwell of the Behavioral Science Building, at 1007 W. Harrison St., around 4 a.m. Friday.

The young woman was not a student, and apparently was hanging out with some friends at the time.

For unknown reasons, she tumbled over the edge of a stairwell railing, falling at least 20 feet.

Her friends, who are believed to be UIC students, called police and tried to save her.

One young man said he performed CPR on her for at least 10 minutes. He said it took first responders at least 10 minutes to arrive.

The victim was rushed to John H. Stroger Jr. Hospital of Cook County, where she was pronounced dead.

The stairwell where the victim and her friends were hanging out leads to an outdoor patio that is popular with UIC students. Beer bottles and cans were strewn on the patio on Friday, but university officials have not confirmed whether alcohol might have played a role in the woman’s death.