UPDATE: Heartbreaking moment mum of kids who died in fire wakes in hospital

UPDATE

A mother who lost three of her four children in a house fire has woken in hospital to the tragic news that her children have passed away. 

Kara Atkins was sedated shortly after she arrived at John Hunter Hospital due burns to her forehead and smoke inhalation.

Her only surviving child, eight-year-old Bayley Atkins, was taken to the hospital’s Ronald McDonald House.

As doctors eased her off the medication the horrific reality of what had happened began to set in, her friend Tash Hunter told The Daily Telegraph.

Ms Atkins had seen her two daughters leave in an ambulance and presumed that they were still alive.

However, her five-year-old twin girls and their brother Blake, 12, all perished in the horrific fire.

"She screamed, 'Why the girls? Please, not the babies,' when the doctors told her what happened at the weekend," Ms Hunter said.

"She’s blaming herself because she couldn’t save them. She’s in deep shock, her mental state is up and down, those children meant everything to her, she’s a wonderful mother, they wanted for nothing, she adored them," she said.

A family member, Britt Rinkin, recently expressed her grief online as the family struggled to process losing the three children.

"To be in that moment when we were told we lost our daughters, son, grandchildren, nieces, nephew and cousins, and to re-hear it on the news repeatedly, to see it on social media is gut-wrenching for our family because we are grieving horrendously," she posted.

She also thanked those across Australia who donated some $237,000 to the family's GoFundMe in the hope that the family can someday rebuild their lives.

Police believe the fire was likely caused by a malfunctioning fireplace that sparked the blaze at 3.30am at the Singleton home in NSW's Hunter Valley.

EARLIER

Firefighters and neighbours were beaten back by flames as they tried to save a family from a house fire in the NSW Hunter Valley that left three children dead.

Authorities are investigating whether the blaze started in the fireplace of the Singleton home in the early hours of Wednesday morning.

Crews broke through windows to rescue two five-year-old girls from their smoke-filled bedrooms just seconds before they were engulfed by flames.

The young pair were rushed to Singleton Hospital but died soon after.

An boy, 11, was later found dead inside the burnt-out home. It's believed the three children were siblings.

First responders managed to save a 31-year-old woman and her son, 8, who were treated by paramedics before being taken to hospital.

The woman suffered burns to her back and forehead and her son was treated for smoke inhalation. Both remain in a stable condition.

NSW Police Superintendent Chad Gillies said it's believed all five lived in the house together.

"I would like to emphasise the heroic nature of the four residents in the nearby vicinity who tried to assist the people inside the house and importantly got the mother and eight-year-old out," he told reporters.

Early investigations suggest the fire started at the front of the house before spreading to the back of the home.

Fire and Rescue NSW Superintendent Joshua Turner confirmed there was a fireplace inside the property, but it was too early to say if it caused the fire.

"The fireplace is one of the factors that will be looked at," he said.

"But obviously during these winter months, heating appliances are quite prominent in fire causes."

Smoke detectors were installed in the home and could be heard by neighbours and emergency crews, he said.

"With the intensity of the fire ... the neighbours and those that attended and tried to assist did a pretty incredible job," Supt Turner said.

Among them was neighbour Brock Forbes, who said he and his family were woken up by a "big bang" and tried to fight the blaze until fire crews arrived.

"(We heard) just smashing and screaming so we ran out and grabbed the hose," he told the ABC.

"I was trying to put the fire out and trying to save them and firefighters came and got it under control."

Police, paramedics and firefighters admitted it was a tough and distressing time for crews, as it was for tight-knit locals.

"We're all in this together," Supt Gillies said.

"These things tear at the heart of a local community like Singleton."

NSW Premier Gladys Berejiklian described it as a "shocking, horrific" accident.

"Our heart goes out to the family and loved ones of those victims," she told reporters in Sydney.

"Can we please ask everybody to be safe, to take all the precautions necessary. We don't want to see any other family experience this horrific tragedy."

This story originally appeared on 7news.com.au.