Hannah Comber (65) suffocated after becoming entangled in the straps binding her to the chair.

When it was discovered that the woman had choked to death, she was removed from the chair, washed, and placed in fresh clothing before gardai arrived. A report, which was given to gardai, failed to accurately outline how the patient died.

A subsequent post mortem conducted by assistant state pathologist Dr Margaret Bolster at Cork University Hospital the following day found that Hannah Comber had died of asphyxiation after being strangled by the ligature on the chair into which she was tied.

The incident occurred on 22 June at Heatherside Hospital near Buttevant in north Cork. Her death notice was recorded in the following day's edition of The Examiner newspaper.

After the woman's death, gardai took statements, but no indication was given to officers that Comber had choked while strapped into the chair unattended.

Gardai launched an investigation immediately after they received the pathologist's post mortem findings.

Gardai re-interviewed staff at the hospital last week. One of the lines of inquiry is whether some staff were asleep when the patient slipped in her chair and her neck became caught in the ligature.

"The report into how the woman died which gardai received did not correspond with what the post mortem revealed. Arising from that officers have gone back to speak with staff at the hospital last week, " a garda source said.

The investigation is expected to be completed within the coming week and a file will be sent to the office of the director of public prosecutions (DPP), the Sunday Tribune has learned.

A spokeswoman for the Health Service Executive (HSE) said it is "cooperating fully" with the garda investigation. The HSE will also be conducting its own investigation into the death.

The dead woman had been a resident at Heatherside Hospital for the past 15 years. The former TB sanatorium is run by the HSE as a continuingcare facility for the South Lee mental health services. The hospital is home to 59 older patients with mental health problems.

The dead woman was unmarried and is survived by three elderly sisters. HSE South spokeswoman Christine Eckersley said: "The HSE has met with the patient's family to extend its deepest sympathy and will keep them informed."

Family members of Hannah Comber contacted this weekend told the Sunday Tribune of their shock in relation to the inquiry into her death.

Her nephew, Tom McGrath, said yesterday, "as far as we are concerned the hospital has always been very good to Hannah. We are very surprised to hear there is a garda investigation into her death."

The woman's niece, Breda McGrath, said she was "shocked" to learn of the probe into the circumstances of how her aunt died.

The garda investigation into the woman's death comes almost a year after the damning revelations in relation to the care of elderly people, arising out of the Leas Cross nursing home controversy. It raised major questions in relation to the use of specific types of restraints to restrict elderly patients' movement.

A report into that matter has not yet been pubished.