Police investigating the apparent murder-suicide of a family of four in Sydney's north are expecting more information to be revealed in toxicology reports.
The bodies of Fernando Manrique, 44, Maria Lutz, 43, and their autistic children, 11-year-old Elisa and 10-year-old Martin, were found in their home in Davidson on Monday.
Police said on Tuesday they were investigating whether the family was gassed, with toxicology reports imminent.
A dog was also found dead in the house, with all family members appearing uninjured, police said.
Media reports suggest an elaborate system of pipes carried the gas into the house via the ceiling.
The Davidson community has been rocked by the shocking event.
The children's school, St Lucy's in Wahroonga, held a memorial service on Tuesday after psychologists were called in to comfort distressed staff and students.
The home remains a crime scene while investigations continue.