THE parents of little Elisa, 11, erected a fence around their northern beaches home after she escaped earlier this year, it has been revealed.

She was gone for five hours before anyone found her. On Monday, Elisa, her brother Martin, 10, and her mother and father Maria Claudia Lutz, 43, and Fernando Manrique, 44, were all found dead.

Their bodies were discovered inside their Davidson home, north of Sydney. Police suspect the family, originally from Colombia, was poisoned in a murder-suicide after gas canisters were found around the home.

A friend of the family, who did not wish to be named, told Bogota-based The City Paper, the escape added pressure on the family who wanted to return to Colombia but couldn’t because “the children could not travel due to their health issues”.

Both Elisa and Martin were autistic.

Mr Manrique was known locally as the loving father who chatted as his two children played with local kids at the park.

He was a high-flying technology executive whose work took him around the world.

But behind the friendly face and the suit-and-tie was a man who turned the family home he built 11 years ago into a gas chamber.

Police were yesterday dismantling the sinister network of hidden pipes used by Mr Manrique to gas his family.

Neighbours who saw him on the roof of the Davidson home with power tools over the weekend had no idea he was rigging up what has been described as an elaborate system to pump gas into the rooms.

Detectives are investigating the source of the poison found in gas canisters as family members in their home city of Bogota, Colombia, revealed the couple, whose son and daughter were both autistic, was on the verge of divorce.

The fiercely protective mother, Maria Claudia Lutz, 43, was found dead in one room with their daughter Elisa, 11, while their son Martin, 10, was found in another room alone.

Engineer and technology expert Mr Manrique, 44, was found on his own in another room. The family’s dog was also dead.

Neighbour Ofik Thomassian, 72, who lives directly across the street, watched Mr Manrique working on the roof on Saturday.

“He was right up on the roof replacing tiles and using power tools of sorts,” Ms Thomassian said.

“He was cutting and banging and making all sorts of noise and pulling up tiles but I don’t really know what he was doing.”

The bodies were discovered on Monday morning when staff at St Lucy’s Catholic School alerted police after the children did not attend class and Ms Lutz did not arrive to run the canteen.

Ms Lutz was last seen on Friday after picking the children before having a coffee with other mothers.

BOC gas employees yesterday inspected the property which was rigged throughout the roof to deliver the deadly fumes in what a police source described as an “extensive, elaborate and well planned” operation.

Police are leaning towards the fact that the Drake Business Logistics company executive acted alone but have not been able to rule out the possibility of a murder-suicide pact with his wife.

“We may never know whether she knew what was happening, we just don’t know,” a source said.

Police are also investigating “domestic tension” between the couple as relatives’ tributes on Facebook pointedly made no mention of Mr Manrique.

A source close to Ms Lutz, who wished to remain anonymous, has told The City Paper in Bogota that the relationship between the couple was “at times very tense due to the stress of bringing-up the children.”

The source said Mr Manrique had “become very distant” and that his wife felt “very alone” but they could not confirm that she was filing for divorce and custody of the children.

Computers were seized from the house to see if Mr Manrique had been researching the gassing and for any hint Ms Lutz knew about it.

Ms Thomassian said he was friendly and she was very protective of the children.

“She would lead them one at a time into the car, lock the door, and return to the house for the next child,” Ms Thomassian said.

“She looked after them but I have to say she never looked happy.

“She always had a very serious look on her face. Thinking back now, she looked like she was in pain. She probably had been for a very long time.”

Police have appealed for public help.

“Police are looking at the possibility the family members died from the introduction of an airborne gas,” a spokesman said yesterday.

“It is early days in the investigation and investigators will need to wait for toxicology results and results of the post-mortems to determine cause of death.”

LOVING MOTHER A FIGHTER TO THE END

By Danielle Gusmaroli

IT was her fight that won Maria Lutz the most admiration; a selfless, dogged ­determination to give some level of normalcy to her two severely autistic children.

That much was abundantly clear yesterday as friends and relatives of the devoted 43-year-old mother honoured her with tributes and praise.

As the Colombian Consulate makes arrangements to fly relatives to Sydney to identify the bodies of Fernando Manrique, his wife Maria and their two children, Maria’s grief-stricken sister Ana Lutz took to Facebook to pen her ­despair, writing: “No one can say anything different than you being a warrior, always fighting for everyone!

“My cute doll … One more angel in heaven, an angel given to their children, life!!”

The deaths of the couple and their two children Elisa, 11, and Martin, 10, have left family and friends reeling as reports emerged that the family was gassed.

Maria had previously told of the sleepless nights and ­battles she endured raising two children who both struggled with non-verbal autism, but frequently told friends they were “my life”.

The couple, who left Bogota for Australia and have no immediate family in the country, arrived in Davidson in northern Sydney in 2005.

Close friend Peta Rostirola described Maria as “selfless” in the battles she fought raising autistic children: “You faced life head on with all the challenges it threw.”

Maria campaigned tirelessly for children with autism and often volunteered at St Lucy’s school’s fundraisers.

St Lucy’s principal Warren Hopley honoured the woman who “touched the lives of so many”. “We are all struggling to come to grips with this profound tragedy,” he wrote.

“Elisa, Martin and Maria have been such a source of ­inspiration for us all at St Lucy’s over the years.

“I have been bombarded with expressions of support and love. Maria touched so many people’s lives.’’