The Western Australian Department of Corrective Services is conducting an urgent review into how an Indigenous woman was left to give birth alone in the cell of a Perth prison last month.

Guardian Australia understands the woman had pressed the cell alarm button and requested assistance but gave birth before either medical help arrived or custodial staff arrived to unlock the cell.

The woman, who was 36 weeks pregnant, had been on remand at Bandyup women’s prison for several months and had been seen by medical staff that afternoon.

She has since been released bail.

In a statement to PerthNow, which first reported the incident, a spokesman said the woman “gave birth very quickly after it was made clear she was going into labour” and that “staff acted as soon as they could to manage the unexpected birth”.

The department is conducting a review of the incident and is expected to ask questions of both medical and custodial staff at the prison, as well as checking the recordings of the woman’s calls for assistance.

The state’s inspector of custodial services, Neil Morgan, said he would await the findings of that review.

Morgan said he became aware of the incident the morning after the woman gave birth and had sent a list of 20 questions to the department.

“I think it is wrong that any woman should be giving birth in a prison cell by herself,” he told Guardian Australia. “What we do need to do is find out exactly what the circumstances of that were and if there were delays what were the reasons for those delays.

“The key thing is we have to ensure that this type of event does not happen again at Bandyup or any other prison in this state, and that any type of medical emergency is responded to quickly. For example if a person is having a heart attack or self-harming in their cell, there must be a timely response.”

It is not unusual for Bandyup to house expectant mothers, and the prison has procedures in place to manage pregnancies.

Morgan said it was the only case he had heard of a woman giving birth alone in a WA prison cell, but added: “The fact that it’s rare doesn’t mean we should not be looking to get to the bottom of what has happened.”

Reports of this incident come just a week after reports of another incident in August last year, when a female prisoner was transported naked and handcuffed from Bandyup to the secure mental health unit at Graylands hospital.

She was menstruating and reportedly arrived covered in blood.

That incident is currently under review by Morgan’s office.

WA has the highest imprisonment rate for Aboriginal and Torres Strait Islander women in the country and also has the highest rates of Indigenous prisoners held on remand, according to Australian Bureau of Statistics figures for the December quarter of 2017.

Indigenous women are the fastest-growing prisoner cohort in the country. A recent report by the Australian Law Reform Commission found that Indigenous women’s imprisonment was driven by exposure to trauma like family and sexual violence, as well as poverty and homelessness.

It found that Indigenous women were the least likely of any group to be able to find stable accommodation upon release from prison, particularly if they have dependent children.

The Department of Corrective Services has been contacted for comment.