The Illawarra Shoalhaven Local Health District and NSW Police are investigating the circumstances surrounding the death of Nikola Nastovski who died ‘’unexpectedly’’ at the Mirrabrook mental health unit on May 4.

ISLHD chief executive Margot Mains said two staff members had been stood down pending a review.

‘’The local health district is currently investigating the circumstances surrounding the unexpected death of a mental health service client earlier this month,’’ she said.

‘’… The health district has extended its sincere condolences to the family at this difficult time, and will continue to provide support and keep them updated.’’

A source told the Mercury the patient voluntarily admitted himself into the mental health unit. He was allegedly found dead in his bed early one morning.

The death has been reported to the coroner. The coroner has requested that police provide a brief of evidence by July 10.

A funeral announcement for Mr Nastovski stated: ‘’Nikola will be sadly missed by his loving family and many dear friends here and in Macedonia’’.

Sources say investigations will focus on whether the appropriate observations and checks were undertaken by staff at the unit.

Observation practices at Shellharbour Hospital’s mental health facilities have come under scrutiny in recent years, after the killing of 47-year-old Joseph Gumley by his roommate at the Eloura West unit in 2014.

Paul Hindmarsh, 31, fatally assaulted Mr Gumley with the dead man's own electric guitar some time between 6.30am and 7.50am on July 31 of that year.

Hindmarsh was found not guilty of murder due to mental illness in February 2016, but was detained under mental health legislation.

A NSW Health report into that incident found the two men were not checked for hours, with investigators told that staff regularly signed observation sheets without actually seeing patients.

Less than 12 months later, in May 2015, four nurses were stood down at the Eloura mental health unit after a female patient was left unchecked and fled in the middle of the night.

The woman was reported missing by staff on duty at the Eloura mental health unit at 2am, and was later returned by police.

On Tuesday Ms Mains said the district’s mental health service had worked hard in recent years to ‘’strengthen the delivery of appropriate clinical care levels and associated observations’’.

This included an education program for staff, as well as random audits to monitor their compliance with observation policies.

Meantime in recent months staff unions have expressed concerns that the hospital’s mental health services will suffer under plans to upgrade Shellharbour Hospital under a public-private partnership.

They claim a private operator would not see a ‘’profit’’ in maintaining these services.