A nurse charged with murder over the fatal nursing home fire in Sydney's north-west was at the scene of the blaze yesterday.

Roger Dean, 35, was arrested last night and charged with four counts of murder over the fire that tore through Quakers Hill Nursing Home.

Dean, who was a nurse at the facility, was remanded in custody after appearing via a video link in the Parramatta local court today.

Police say they expect to lay more charges against the nurse, who will face court again next Thursday.

Before his arrest, Dean spoke to the media assembled at the scene of the devastating fire, saying he was involved in the rescue.

Three residents died in yesterday morning's fire at Quakers Hill, and a fourth resident died in hospital later that day.

Police now say a fifth resident has died, leaving 10 elderly people still fighting for life in intensive care units across Sydney.

Prime Minister Julia Gillard says it is a dark day for many families.

"To imagine frail, elderly people caught up in a fire like that, at risk of being engulfed by flames, is truly horrifying," she said.

"My condolences do go to the families who have lost loved ones and to those whose loved ones are now in hospital."

Detective Superintendent Mike Willing from the Police Homicide Squad says Dean was questioned for several hours overnight and charged early this morning.

"All I can say is that last night detectives were speaking to the man at Mt Druitt Police Station where they formed the opinion that they had sufficient evidence to place him under arrest," he said.

"They did so and at the conclusion of an interview he was charged with four counts of murder."

Police say say Dean is a registered nurse and an employee of the burnt down centre. He also lives in Quakers Hill.

Investigation underway

Detective Superintendent Mike Willing from the Police Homicide Squad says forensic officers are working in tough conditions at Quakers Hill today.

"This investigation has had an impact on all of the investigators. This is a tragedy for Sydney, it's a tragedy for the entire community," he said.

He says investigators are still trying to piece together the evidence.

He says they have also spoken to other staff members at the nursing home.

"We spoke to them about their knowledge of the circumstances around the fire and their knowledge of how the fire occurred, if they had any knowledge of that, and certainly those details will come out, they are all wittinesses that will be dealt with in court proceedings," he said.

It is believed there were two separate ignition points at the nursing home, but investigations have been hampered by the unstable condition of the building.

Forensics officers began dusting the scene for fingerprints soon after the fire was extinguished yesterday, as firefighters shored up the damaged part of the building so investigators could enter.

Trained police dogs sniffed the scenes for traces of accelerant like petrol.

Flowers have also been laid outside the home for the victims.

A firefighter dampens down a section of the Quakers Hill nursing home. ( ABC TV )

Frantic search

Yesterday family members of residents were frantically trying to track down their loved ones.

Melinda Champion, office manager of Quakers Hills Anglican Church, said some of the residents had been taken to the church where many were being met by relatives.

"We've got a lot of their family members here as well so they're very comfortable. It's been quite good that we've been able to match family members with patients," she said.

"There's also a few that have turned up looking for their family and unfortunately their family hasn't been here - they've been moved to other nursing homes or to hospitals."

Gary Barnier, chief executive of Domain Principal Group which runs the nursing home, said he had met families of those affected by the fire to express his condolences and offer them support.

Federal Minister for Ageing Mark Butler said affected residents would be moved to alternative aged care facilities.

He says the Quakers Hill home only recently met accreditation and safety standards.

"The facilities are also required to have regular audits of their fire safety systems conducted by independent auditors," he said.

"I'm advised that this facility had an audit of their fire safety systems as recently as July and again was found to be compliant."

People who have friends or relatives at the nursing home are being asked not to go to the scene but instead call 1800 227 228 for more details.