Post-mortem examinations have confirmed the cause of death of five members of the same family found bludgeoned in their Sydney home, police say.

Newsagency owner Min Yin, his wife Yun Li Lin, the couple's sons Henry, 12, and Terry, nine, along with Ms Lin's 39-year-old sister Irene Yin were found dead in their beds at an Epping address on Saturday.

Investigators are yet to determine a motive for the brutal killings, which left each victim unrecognisable.

"I'm not at liberty to comment any further on the detail of the post-mortem results because the further analysis of those results is taking place as we speak," NSW Police homicide squad boss Detective Superintendent Geoff Beresford told reporters on Friday.

"Suffice to say that we do know that all of the members of the family suffered severe blunt force trauma."

The couple's surviving 15-year-old daughter Brenda and other relatives had spoken with police, including many who had travelled to Sydney from China, Det Supt Beresford said.

"They wish to thank the media and they wish to thank the community for their support, but they certainly ask for privacy in this time of grief and they may be able to make a statement later this week," Det Supt Beresford said.

A large number of items have been taken from the family home for forensic testing.

But police would have to wait weeks for any results from the items as well as from toxicology tests from the autopsies, he added.

"(The post-mortem examination) has provided us with a particular cause of death, but what you have to understand is that we haven't been able to formally identify any of the family members at this point ... visual identification is not possible," Det Supt Beresford said.

Forensic examiners have completed their work at the crime scene in Sydney's northwest, but detectives are continuing their operation at the home.

SMH