Horrifying details emerge after three-year-old girl was found dead in cockroach-infested unit

A coroner is investigating the death of a three-year-old girl found lying unresponsive in a cockroach-infested unit with rotting food in the kitchen and clumps of the girl's hair all over the floor.

Deputy State Coroner Joan Baptie will be asked to examine if the Department of Communities and Justice failed in its dealings with the family over the alleged neglect of the young girl, who cannot be named for legal reasons, before her death on May 30, 2018 in northern NSW.

Counsel assisting Chris McGory told the inquest on Monday in Newcastle that an autopsy revealed the girl's cause of death was bilateral bronchopneumonia.

But Mr McGory said the girl had also been suffering from renal failure and an extreme infestation of head lice.

The girl's mother had left clumps of the girl's hair on the floor throughout the two-bedroom unit when attempting to get rid of the head lice.

Mr McGory said the girl and her younger brother had been living alone in the unit with their mother who had little community support to help raise the children and was quite isolated.

The children's father would visit them regularly but was struggling with mental health issues.

The girl had been enrolled for pre-school but was not attending before her death.

Mr McGory said the mother believed the girl had had a cold about two or three weeks before she died.

The girl became ill again in the week leading up to her death with cold-like symptoms including a dry cough, sore throat, feeling lethargic and having a reduced appetite.

On May 30, 2018, the girl was given a drink of milk about 7am before going back to sleep.

A case worker from the Benevolent Society's Brighter Futures program (now known as Family Preservation) had been scheduled for a home visit that day but the mother cancelled the appointment because the girl was sick.

No one had been to see the family since May 1 despite the case worker contacting the mother by phone or text during the month trying to set up a visit.

The mother called a medical centre about 8.30am and arranged for her daughter to see a doctor at 2pm.

The father came to visit and went out to buy some Nurofen and cough medicine for the girl about 9.20am.

Mr McGory said the mother believed her daughter had a viral illness and did not understand her condition was 'life-threatening'.

When the mother could not wake the girl just before 2pm, she put her in the shower but she was unresponsive.

The father called triple zero and the operator gave the distraught parents instructions on how to use CPR on the girl but she could not be revived.

Paramedics arrived at 2.09pm to find the parents in a 'highly distressed state'.

Mr McGory said the girl was lying on her back in the lounge room unresponsive, cold to the touch and not breathing.

She was taken to hospital but declared dead at 2.43pm.

The unit was described as being very messy in an unhygienic state with rotting food in the kitchen, clothes strewn throughout the living areas and infested with cockroaches.

Mr McGory said the girl's head lice was so extreme it was indicative of how parental care had unravelled or deteriorated by that stage.

He said in the 12 months leading up to the girl's death, the department and Benevolent Society had had dealings with the family and it was expected the coroner would examine the response by both institutions to what had been unfolding.

Mr McGory said the coroner would also want to look into the department's decision to close the file on the family and refer the case to the Benevolent Society.

The inquest continues.