Australian police are trying to establish how three people died and a fourth became critically ill after apparently eating wild mushrooms at a family lunch.

Police have interviewed the woman who they say cooked the meal at her home on July 29 but did not become ill herself. Police released her without filing any charges but say she remains a suspect.

The woman told media outside her home in the town of Leongatha, in Victoria state, that she did not know what had happened.

“I didn’t do anything,” she told Network Nine on Monday. “I loved them and I’m devastated they’re gone.”

The woman declined to answer questions about what meals were served to which guests or the origin of the mushrooms.

Victoria Police Detective Inspector Dean Thomas said it was not clear what type of mushrooms the guests had eaten, but their symptoms were consistent with those from a death cap, a particularly deadly variety.

He said it would take some time to determine what happened and police were keeping an open mind.

“It could be very innocent but, again, we just don’t know,” Mr Thomas said.

The woman had been hosting her in-laws, Gail and Don Patterson, both aged 70. Both died at area hospitals.

Also at the lunch were Gail Patterson’s sister Heather Wilkinson, 66, who died, and husband Ian Wilkinson, 68, who remains in hospital this week in critical condition.

Mr Thomas said the woman who cooked the meal was separated from her husband but police had been told their relationship was amicable. Her children were also at home during the lunch but did not eat the same meal, police said.

Detectives searched the woman’s home on Saturday and took several items. The Sydney Morning Herald reported that police were also conducting forensic tests on a food dehydrator they had found at a nearby landfill to see if it was linked to the case.