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.

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 when 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.

Police did not say if the door to the roof locked behind the woman or explain why she didn't get back inside. But Kraus said an alarm on the fire door did not go off, which would have alerted staff that Diggs had exited.

The hospital's statement confirmed the death and identified the woman's last name as Biggs. But Kraus said he read the woman's hospital wrist band identifying her as Diggs, and her family has confirmed that last name.

Police have interviewed the family and they were meeting with social workers at the hospital, Kraus said.

An attorney representing Diggs' family pulled no legal punches when he spoke with reporters outside of the hospital on Wednesday.

"The family is concerned that somebody suffering from dementia was allowed to wander without being closely monitored," said attorney Rob Pierce. "The family is looking to us to try to get to the bottom of the situation to determine how their loved one passed away in such a horrific manner."

According to Pierce, hospital officials waiting 45 minutes before notifying police of Diggs' death. He said hospital officials knew her history of dementia, saying Diggs reportedly wandered away Tuesday in the hours before she went missing.

"There is evidence that she wandered away, and hospital officials failed to take the necessary precautions," said Pierce.

Millie Poindexter, who knew Diggs when the two shared a home in Homewood, said she is praying for the family.

"She should have been watched," Poindexter said.