The dead woman, believed to be in her 70s and from the north Cork area, was a patient at St Stephen’s Hospital, Sarsfield’s Court in Glanmire, Co Cork.
It is understood she was found by staff at the psychiatric hospital last Sunday afternoon and was taken to Cork University Hospital, where she died yesterday.
Superintendent Pat Sheahan said detectives were awaiting the full results of a postmortem, which would determine if they were dealing with an accident or foul play.
The woman was one of approximately 120 patients at the hospital.
The HSE issued a statement last night which confirmed it is also investigating the elderly patient’s death.
A HSE spokeswoman said that a patient at the hospital had died “after what appears to have been a tragic accident”.
The spokeswoman added that hospital staff had “acted quickly” to provide medical attention when they discovered the situation and the patient had been brought by ambulance to CUH.
“Sadly the patient died,” the spokeswoman added.
She said the HSE (South) had contacted the patient’s family, the gardaí and the Mental Health Commission and “will co-operate with any investigations that are deemed necessary”.
The dead woman’s name has not been released by either the gardaí or the HSE.
The HSE is also carrying out its own examination of the circumstances behind the elderly woman’s death.
“The HSE extends its deepest sympathy to the patient’s family and will continue to offer support to all those affected by this incident,” the spokeswoman said.
St Stephen’s Hospital is one of the largest psychiatric units in the south of the country.
Most of its patients come from the north Cork area, from as far as Charleville and Watergrasshill.
Several are long-stay psycho-geriatric patients, but the hospital also deals with a number of younger people who have temporary mental problems.