A family of four, including two children with "significant disabilities", has been found dead in a home in Sydney's north, in what police have described as a "tragic" and "horrific" event.

Key points: Parents were foreign nationals and both children had autism

Parents were foreign nationals and both children had autism A "large dog" also found dead at the house

A "large dog" also found dead at the house Police have not disclosed the cause of death

Officers attended the home on Sir Thomas Mitchell Drive at Davidson about 11:20am on Monday following reports concerning the occupants' welfare.

Northern Beaches Police Superintendent Dave Darcy said officers found a 43-year-old female, a 44-year-old male, a 10-year-old boy and an 11-year-old girl dead at the home.

The family has been identified as Colombian nationals Maria Claudia Lutz and Fernando Manrique, and their children Elisa and Martin.

Superintendent Darcy said "a large dog" was also found dead at the house.

Fernando Manrique with his daughter Elisa. ( Facebook: Fernando Manrique )

Superintendent Darcy described the incident as a "tragic" and "horrific thing". He said "both children suffer a significant disability".

The ABC understands the children had autism.

"It's extremely confronting, the officers — we consistently have these concern for welfare cases, and unfortunately in some cases this is what the police are confronted with," Superintendent Darcy said.

"We have now commenced a thorough investigation, homicide squad are here with us, forensic services group are here.

"And we're gradually working our way through a very tragic circumstance to get to the bottom of it."

He said neither of the adults were known to police.

Mother held in high regard: police

Superintendent Darcy said the situation was "very serious".



"Two young children have died, two adults have died, I just want to keep this investigation … untainted so our investigators can clearly and concisely get the information they need to come to the truth of what's happened," he said.

"The mother in particular is held in very high regard in the community.

"Since coming to Australia they've made a significant contribution to how we live, they've done a fantastic job."

Police closed a street in Davidson after discovering four bodies. ( ABC News: Richard Hoskins )

Superintendent Darcy said he was not willing to discuss the cause of death or the nature of any injuries.

A section of the leafy suburban road was cordoned off restricting access to the house.

School, neighbours shocked by death of family

The children went to St Lucy's primary school in Wahroonga.

Acting principal Warren Hopley said staff were in shock.

"The teachers today … we're just all very upset," he said.

"The children had very high complex needs … I don't think [their mother] slept for many hours of the night because of the difficulties often with the two children."

Neighbours said the children were lovely and kept to themselves.

Shaun Daley said he was sitting inside watching TV when he heard an ambulance go past.

"I thought nothing big of it — someone's just hurt themselves or something, I didn't really think it was quite to this extent, and then police started turning up and it built from there," Mr Daley said.

"They closed off the road and everyone was trying to find out what was going on, we heard about the family of four and the dog, which was really shocking to hear.

"Davidson's very quiet, it's so unexpected, especially around here, very shocking."

Calvin Barker, another local man, said he was he was saddened by the event.

"Nothing's really happened, this intense, forever, actually."