Gas bottles were found inside a Sydney home where a mother, father, and their two autistic children were found dead, as police confirm they are not looking for a suspect.

It is believed an odourless carbon monoxide gas was administered through an elaborate system to spray gas through the house to kill Fernando Manrique, his wife Maria Lutz and their children Elisa, 11, and Martin, 10, according to The Sydney Morning Herald.

The family were found at their home in Davidson, in north Sydney, dead in an alleged murder suicide. The family dog was also found dead at the scene.

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Flowers have been laid outside the family home as devastated friends pay their respects to a Sydney family found dead in their house

The coroner was seen carrying each of the family members, identified as Fernando Manrique, 44, Maria Claudia Lutz, 43, and their children Elisa, 11, and Martin, 10, (pictured) who died alongside their pet dog

Ms Lutz is pictured with her 10-year-old son Martin and 11-year-old daughter Elisa

The bodies of the family were removed from their north Sydney home on Monday night

Pictured is the Sydney home where a mother, father, and their two autistic children were found dead after being gassed in an apparent murder-suicide

Mr Manrique is believed to have installed the gas system through the house when he was spotted working on the roof with power tools two days earlier,The Daily Telegraph reported.

'Whilst the cause of death will be a matter for the Coroner to determine, police are looking at the possibility the family members died from the introduction of an air-borne gas,' police said in a statement on Tuesday.

Ms Lutz was discovered in a room with one of her children, while her other child was found in a separate room. Mr Manrique was in a different room on his own.

Daily Mail Australia has been told 'toxic paraphernalia' was found in the kitchen of the Sir Thomas Mitchell Dr home, when police forced their way in looking for the young family who had failed to turn up to work and school commitments.

Police on Tuesday said 'extensive forensic testing' would be carried out on the bodies during post-mortem examinations, to establish exactly what killed the family of four.

According to The Daily Telegraph, the young family are believed to have been gassed to death after numerous gas bottles were found scattered around the home.

'There was a lot of pre-planning that went into this', a police source told the publication.

Investigators are now looking in to where the gas bottles were purchased.

Neighbour Okik Thomassian, 72, who lives directly across the street said he often spoke to Mr Manrique, who regularly did work on the house with power tools.

The elderly woman told the Daily Telegraph she last saw him just two days before his death.

It is understood the Colombian Consulate is making arrangements with relatives to fly to Sydney to identify the bodies and make funeral arrangements.

Mourners have been seen laying flowers outside the house

Gas bottles were found inside the home with police confirming 'toxic paraphernalia' was found in the kitchen

It is understood the Colombian Consulate is making arrangements with relatives to fly to Sydney

A message outside St Lucy's School where the two children attended

'We will be meeting with relatives in the coming days to answer their questions,' a police spokesman said.

Ms Lutz's sister, Ana Lutz, said she was 'a warrior'.

'Always fighting for all,' she wrote on social media, according to Facebook translator. 'My cute doll.. One more angel in heaven, an angel given to their children.'

FROM COLOMBIA TO SYDNEY: A TIMELINE Early 2005: Fernando Manrique and Maria Claudia Lutz move to Sydney, Australia from Colombia. February 2005: The couple purchase a home in Davidson, in Sydney's north, for $590,000. May 2005: Their first child Elisa is born. August 2006: Mr Manrique and Ms Lutz's son Martin is born. Both their children have non-verbal autism. January 2009: Ms Lutz's parents visit the family in Sydney. November 2009: Ms Lutz's brother and sister-in-law travel to Sydney for a holiday. 2012: Elisa starts school at St Lucy's School for children with disabilities in Wahroongah. 2013: Martin starts school at the same place. Their mother was a regular helper at the school canteen and well-liked within the community. November 2013: Mr Manrique starts work at Drake Business Logistics as Chief Technology Officer. May 2015: He is named the Executive Director of Drake Business Services Asia. The father frequently travels for work with this new role. October 2016: Family and their pet dog found dead at their home. Believed to have been deliberately gassed. Advertisement

Mr Manrique worked for Drake Business Logistics as the Executive Director of their Asia Services branch.

He was 'actively involved in re-engineering and company mergers, where he has used his expertise and engineering training to successfully bring operational and strategic goals together'.

Vanessa Parker, National Manager for Strategic Communication at Drake International, said the company was 'extremely distressed' by the news of his death.

'We are obviously extremely distressed by the recent news, and our thoughts are with everyone who has been affected,' Ms Parker told Daily Mail Australia.

Ms Lutz had studied at private all-girls school Gimnasio Feminino in Bogota, according to Colombian media.

She went on to study law at Nuestra Señora del Rosario university.

Mr Manrique studied at all-boys school Gimnasio Campestre, City Paper Bogota reported.

He finished an MBA (Master of Business Administration) at Macquarie University and then began work at Fuji Xerox Australia before moving to the Drake Business Logistics.

Mr Manrique frequently travelled around Asia for work, and was supposed to be in the Philippines with his business partner.

It is understood his partner has now flown back to Sydney following the tragedy.

Meantime, a prayer service will be held for the family on Tuesday, a spokesman for the Catholic Education Commission NSW said.

It is understood police are investigating if the family was poisoned after police said no signs of violence were found in the house

Maria Manrique (centre), 43, is pictured with her children Fernando Manrique, 44, and children 10-year-old Martin (right) and 11-year-old Elisa (left)

A crime scene has been established at the home but police have not confirmed how the family died

The school has offered counselling for the teachers and students.

On Monday evening the bodies of the family were removed from their home.

The coroner was seen carrying each of the family members, identified as Mr Manrique, 44, Ms Claudia Lutz, 43, and their children Elisa, 11, and Martin, 10, who were both autistic, from their Davidson, north Sydney, home after 10pm.

Police are treating the deaths of the parents, originally from Colombia, and their children as a murder-suicide and are investigating if they were poisoned as there were no signs of violence at the scene.

Ms Lutz, 43, and her husband, who moved to Sydney from Colombia in 2005, disagreed on how to parent their children, both of which had nonverbal autism and were unable to speak.

Neighbour Shaun Mayatt said lots of work had been done on the house to make it safe for the children, Sydney Morning Herald reported.

Neighbour Ofik Thomassian, 72, told News.com.au the father was 'very friendly' and the mother was 'very protective of those children'.

Police received a welfare report for the family about 11.20am after Ms Lutz failed to show up to work at the canteen for the school her children attended

Police were still at the scene late on Monday night (pictured)

'She would lead them one at a time into the car, lock the door, and return to the house for the next child,' the neighbour said.

Ms Lutz is believed to have spent many sleepless nights caring for her children, who needed frequent therapy and doctor's appointments.

She often posted about her children on social media and said her 'worst nightmare' was either of her kids getting lost or going missing.

Police received a welfare report for the family about 11.20am on Monday after Ms Lutz failed to show up to work at the canteen for the school her children attended.

Police forced their way into the home at Sir Thomas Mitchell Drive and found the family of four, and their dog, dead.

Principal Warren Hopley of St Lucy's Primary School in Wahroonga said the mother had coffee with a group of school mothers on Friday and seemed perfectly fine.

The 43-year-old dropped the children off and picked them up every day, he said.

When she and the children did not appear at school on Monday, Mr Hopley said he knew something was wrong.

Police forced their way into the home (pictured) at Sir Thomas Mitchell Drive in Davidson and found the family of four, and their dog, dead

St Lucy's School in Wahroonga also told police the children, who both had non-verbal autism, did not arrive for school

Northern Beaches Local Area Command Superintendent Dave Darcy said it was too early to say whether a murder-suicide had taken place

WHAT IS NONVERBAL AUTISM? Nonverbal autism is described as having the ability to speak but not the language skills to do so in a meaningful way. Others cannot verbally communicate, but instead use typed language or sign language to communicate, as well as nonverbal cues like facial expressions and body postures. It is suggested speech therapy, music therapy and using tools like picture cards and sign language can help build language skills. Source: Very Well and Autism Speaks Advertisement

After repeated unanswered phone calls to their home and no email from Ms Lutz saying her children would not be attending school, a teacher called the police.

Mr Manrique worked for a logistics company, where he had been the chief technology officer for four years.

His business partner Grant Mackenzie said he is currently visiting the Philippines and had been expecting Mr Manrique to join him.

Neighbours said the family were 'normal' and the children would often play in the family's front yard but they 'didn't speak at all,' according to The Daily Telegraph.

'He [Mr Manrique] built them a little play area so they could play in the front garden,' neighbour Sonja Perry said.

'The dad more or less built the house himself. They were well looked after.'

The family of four is pictured during an outing, years before they were all found dead in their home

44-year-old Mr Manrique (pictured) worked for a logistics company

The pet dog was also found at the scene at their family home on Thomas Mitchell Drive, Davidson

The family dog was found dead alongside the family of four

Mr Hopley said Elisa and Martin, who were in year five and year four, respectively, were much-loved students by their peers.

'This is an exceptional family. They've been at the school here for six years. Two beautiful children. And mum was very active within the school - almost a cornerstone of the school in many ways,' Mr Hopley said.

'When all the children leave at the end of the day she would be out there at the exit waiting for her kids and knew the names of every child in the school.

'I don't think she slept for many hours of the night because of the difficulties often with the two children, and yet she would always be here helping out in every way she possibly could.'

Mr Hopley said he wasn't aware of any issues in the family.

'There was no inkling of any of this.'

He spoke to the mother most days and says she was always positive, happy, friendly with other parents and greeted all 140 pupils by name.

The school's teachers were all upset and in shock, an emotional Mr Hopley said.

'The children had very complex needs so you become very attached to them,' he said.

'This was an enormous, enormous shock. It was terrible.'

The children were always active and friendly.

'The girl would often grab me by the hand and take me for a walk,' Mr Hopley said.

'She had a very, really lovely personality and so did (her brother).'

Neighbours said the family were 'normal' and the children (pictured) would often play in the family's front yard but they 'didn't speak at all'

'He [Mr Manrique] built them a little play area so they could play in the front garden,' neighbour Sonja Perry said

Mr Manrique and wife Ms Lutz moved to Australia in 2005 from Colombia

Police said there was no evidence of violence within the home

Principal Warren Hopley of St Lucy's Primary School in Wahroonga said the mother had coffee with a group of school mothers on Friday and seemed perfectly fine

'The staff are all very upset ... and of course now we have to look at ways to talk to the children about this,' he said.

Mr Hopley said counsellors had been arranged to be at the school on Tuesday to support staff and students.

In a Facebook post last year, Ms Lutz had called Elisa a 'princess'. She often campaigned for awareness about autism.

On Autism Awareness Day in April last year, Ms Lutz said 'people with autism have the [same] needs and desires as you and me but they just see life in a different way. They think freely.

'Today we celebrate their life and we try to educate our society to be caring and patient with those with autism. My kids have taught me that giving small steps will take me to where I want to go and I will enjoy the journey even more.'

44-year-old Mr Manrique (pictured) worked as his company's chief technology officer for four years

Mr Manrique is pictured with 11-year-old Elisa

44-year-old Mr Monrique, the father found dead with his wife and two children, is pictured

A neighbour who had just returned home on Monday afternoon said the news was a 'massive shock' to the 'quiet neighbourhood'.

'Obviously you don't know what goes on behind closed doors. Everyone has their own issues,' he said.

'Just to come home to something like this, it's horrible.'

On Monday afternoon, police held a press conference and said they were not yet revealing how the family died, but it is too early to be 'coming to conclusions'.

Northern Beaches Local Area Command Superintendent Dave Darcy said the scene was 'extremely confronting' for police.

Superintendent Darcy also said the mother was in 'very high regard in the community' and the family had 'made a significant contribution to how we live'.

Police released a statement saying a crime scene had been established and will be examined by forensic officers.

A report will be prepared for the Coroner.

Contact: lifeline on 13 11 14.

Warren Hopley (pictured), the principal of Catholic primary school St Lucy's in Wahroonga, said the children had 'wonderful personalities' and 'were always active'

'Obviously you don't know what goes on behind closed doors. Everyone has their own issues,' a neighbour said