PITTSBURGH — An 89-year-old dementia patient, wearing just a gown and slippers, wandered out onto the roof of a hospital and died in the freezing overnight temperatures, police said.

A UPMC Montefiore hospital worker found Rose Lee Diggs, who had last been seen Tuesday evening, unresponsive on the roof at about 9:15 a.m. Wednesday. Overnight temperatures in Pittsburgh dipped into the 20s.

"Medical staff, when they found her, brought her back into the hospital and performed aggressive resuscitative procedures and were unable to revive her," police Lt. Kevin Kraus said.

Kraus said there were no signs of foul play, but that police plan to consult with the district attorney about whether criminal charges are warranted relating to Diggs' leaving the hospital unnoticed. Diggs was suffering from exposure when she was found, the hospital said in a statement.

The hospital said it was reviewing its policies and procedures to prevent a similar incident and was cooperating with police. Officials also said they had reported the incident to appropriate regulatory and government agencies and would seek their input in the hospital's review.

It was unclear whether Diggs, of Pittsburgh, was already dead when she was discovered, Kraus said. The Allegheny County Medical Examiner was expected to conduct an autopsy Wednesday.

Diggs was last seen in her room by a nurse at about 5 p.m. Tuesday, and hospital officials called police less than an hour later to say they could not find her, Kraus said.

"We actually assembled some fliers that were distributed at and around the hospital last night," Kraus said. "And then we were called this morning and they (hospital officials) said she had been located."

Kraus said hospital officials did not immediately tell police the woman had died Wednesday morning. Police learned that only when they followed up on the report that she had been found, Kraus said.

In addition to dementia, Diggs was being treated for heart problems, police said, without specifying.

Kraus said investigators believe they have discovered the path the woman wandered: through a fire exit, up some stairs, through a boiler room and then outside onto the roof. Her hospital room was on the 12th floor, immediately below the roof, Kraus said.