The families of three people who died after eating a poisonous mushroom lunch have been forced to wait for further police inquiries before they can bury their loved ones.

Erin Patterson, 48, cooked a beef wellington at her home in Leongatha, in Victoria's Gippsland region on July 29, that contained death cap mushrooms.

Her former in-laws Gail and Don Patterson, Gail's sister Heather Wilkinson and Heather's husband Ian Wilkinson were all at the lunch.

Gail, 70, Don, 70, and Heather, 66, have all since died, while Ian, 70, has been in a serious condition since the meal.

Heather and Ian Wilkinson (above) attended Erin Patterson's fatal beef wellington lunch on July 29 - Heather died from mushroom poisoning while Ian remains in critical condition

Don and Gail Patterson (above) died after eating lunch at their former daughter-in-law Erin Patterson's home

But it has now emerged that he is slowing improving and may no longer need a liver transplant, according to the Herald Sun.

His recollection is said to be key to the police investigation, which Victoria Police have previously said will be long and complex.

It is unclear how long the grieving family members of the three dead lunch guests will have to wait for further police inquiries into their deaths.

'The deaths are still being treated as unexplained,' a police spokesperson said.

Investigators have also said Erin remains a person of interest.

She has denied any wrongdoing and Daily Mail Australia is not suggesting she is responsible in any way for the deaths poisonings.

It is also not suggested that detectives suspect she is responsible, only that she is a person of interest.

Erin's ex-husband Simon Patterson was initially invited to the lunch but pulled out at the last minute.

Erin Patterson, 48, had cooked a beef wellington for a lunch at her home in Leongatha, in Victoria's Gippsland region on July 29, that allegedly contained death cap mushrooms

The Korumburra community gathered at St Joseph's Catholic Church for a vigil on Saturday

The above family tree shows the connections between the Pattersons and Wilkinsons embroiled in the unusual poisoning tragedy in Leongatha

In a police statement by Erin she claims to have bought the mushrooms used in the beef wellington from a supermarket and an Asian grocer shop in Melbourne - but couldn't recall the name.

She earlier told The Australian she felt like she'd been painted as an 'evil witch'.

'I can't have friends over. The media is at the house where my children are at. The media are at my sister's house so I can't go there. This is unfair,' she said.

It comes as the Korumburra community gathered at St Joseph's Catholic Church for a vigil on Saturday.

Parishioner Ken Loughnan said the church wanted to offer a place for people to 'come together' after a difficult three weeks for the town.

'When a tragedy happens in a small community it has a real hurt and that's been the case in Korumburra,' he said.

'We hope that the sadness felt by the community can dissipate over time'.