A staff member at a San Francisco hospital found an elderly woman who suffered from dementia dead in a stairwell on Wednesday after she disappeared from a mental health institution.

Ruby Andersen, 75, was found in a stairwell of a power plant at Zuckerberg San Francisco General Hospital. Andersen, who had dementia and wore two hearing aids, was last seen May 20. 

Andersen’s daughter, Charlene Roberts, said her family almost hired a private investigator to find their relative, reported KRON-TV.

An autopsy is pending.

"I don't know how she died," Roberts, told KRON-TV. "Did she have a stroke or fall? I don't know what happened."

Hospital spokeswoman Rachael Kagan said while the woman was not a patient at San Francisco General, she may have been a patient of one of the other facilities housed on the same campus — this includes a 47-bed Mental Health Rehabilitation Center.

"We're very concerned that this happened and we don't know how this woman gained access to where she was found," Kagan said, according to CBS San Francisco.

This marks the second time a patient has been found in the stairwell of the hospital.

In Oct. 2013, 57-year-old Lynne Spalding was found dead in the hospital stairwell after she was admitted to the hospital two days earlier, CBS San Francisco reported.

According to a report by the city's medical examiner's office, Spalding had been dead for some days before being discovered. Her death was ruled accidental, due to an electrolyte imbalance, a condition that can be caused by dehydration.

Spalding's family filed a lawsuit against the city of San Francisco, which settled the suit for $3 million. After Spalding's death, the hospital put a set of new security protocols in place.

"That was a terrible tragedy. We've made many, many changes since that time and we have no reason to believe that this case and that case are connected, but we don't know very much about this situation yet," Kagan said.