The South Metropolitan Health Service is investigating the protocols that follow the death of patients in hospital.
That investigation comes after a man in palliative care died in Rockingham Hospital on September 5.
A senior nurse confirmed the man was dead and contacted his family, who then visited the body, which remained on a ward.
The Health Service said that, about five hours later, the man's body was taken to the morgue and the following day a death certificate was completed after a doctor who had been treating him inspected the body.
South Metropolitan Health Service chief executive Paul Forden said the certificate was not done on the night due to a mix-up.
He said the doctor on duty received notifications of two separate deaths simultaneously and did not realise there were two bodies for them to check.
In a statement, the health minister, Amber-Jade Sanderson, said she was concerned by allegations reported in the media that the man may not have been dead before going to the morgue.
"I am concerned about these serious allegations and requested an urgent briefing from South Metro Health Service (SMHS), who have advised that an investigation is underway," she said.
"SMHS is in contact with the patient's family. For the sake of all staff involved — and, importantly, the family — it is important that we allow the investigation, and any external investigation, to run its course.
"I would ask media to respect the family's request for privacy at this time."
A spokeswoman for the minister said she was confident in assurances from the health service that the man was indeed dead before going to the morgue.
"Please let me be very clear, having seen the media [on Thursday], the investigation is into the protocols following the death of a patient, not into whether that patient was deceased," Mr Forden said.
Mr Forden said that, after the family queried why the date on the man's death certificate was listed September 6 rather than September 5, the doctor who issued it was asked to consider changing it.
He said that, when this did not happen, the doctor was then asked later asked why it had not.
"But once he said he did not want to [change it], that is perfectly acceptable," he said.
Mr Forden denied requests to change the date were made as any form of cover-up.
A spokesman for the Coroner's Court also provided a statement on Thursday.
"After receiving notification from a doctor at the Rockingham Hospital of the death of a 55-year-old man, the Coroner's Court on Monday October 3, commenced to investigate whether the death is a reportable death," he said.
"The court does not make public any of those investigations."
Mr Forden said senior colleagues he had spoken to say there was nothing remarkable in what the doctor had written to the coroner.
The President of the Australian Medical Association in WA, Dr Mark Duncan-Smith, has called for the investigations to be full and thorough.
