A body discovered in a San Francisco hospital stairwell was that of a female patient at the facility who disappeared more than two weeks ago, hospital officials said Wednesday.

San Francisco General Hospital Chief Medical Officer Todd May said at a news conference that officials were still awaiting confirmation on the identity from the medical examiner's office. But he said hospital officials had enough information to conclude it was 57-year-old Lynne Spalding's body.

Sheriff's officials don't know how she died or how long she had been in the stairwell, Assistant Sheriff Paul Miyamoto said.

May also said he did not know how Spalding ended up in the stairwell.

"What happened at our hospital is horrible," May said. "We are here to take care of patients, to heal them, to keep them safe. This has shaken us to our core. Our staff is devastated."

Spalding was being treated at the hospital for an infection when she disappeared Sept. 21. Her body was discovered Tuesday.

The stairwell is a fire exit that has an alarm on it, and is locked from the outside, Miyamoto said. It exits onto hospital grounds.

Miyamoto said a member of the hospital's engineering staff found Spalding while conducting a routine quarterly check.

"All of us are committed to learning what happened and insuring it never happens again," he said.

Spalding was last seen two days after she was admitted to the hospital. Friends say she was very thin and frail, was on medication and probably was very confused. A missing persons report was filed with police, who have been investigating her disappearance.

The Sheriff's Department, which provides security at the hospital, will investigate the facility's internal security measures, Miyamoto said.