Erin Patterson, 48, cooked the beef wellington at her home in Leongatha, a small rural town southeast of Melbourne, Victoria, Australia.

It is suspected the four people were served mushrooms known as death caps - which are responsible for 90% of all toxic mushroom-related fatalities.

In a written statement to police, seen and reported by the Australian Broadcasting Corporation and The Age, Ms Patterson detailed what happened before and after the lunch.

She said she wanted to "clear up the record" because she was "extremely stressed and overwhelmed by the deaths of my loved ones" and was hospitalised herself after eating the meal.

Ms Patterson said she had "absolutely no reason to hurt these people whom I loved".

Her former in-laws Don and Gail Patterson, both 70, were among those who ate the meal on 29 July.

They, and Gail Patterson's sister Heather Wilkinson, 66, became ill and later died.

Mrs Wilkinson's husband, Reverend Ian Wilkinson, 68, remains in a critical condition in hospital.

Her former spouse, Simon Paterson, who nearly died from an unknown gut malady last year, has claimed he "suspects" she was trying to poison him.

According to her statement, Ms Patterson served the meal and allowed the guests to choose their own plates. She then took the last plate and ate some of the beef Wellington herself.

She said she suffered bad stomach pains and diarrhoea after the meal and was hospitalised, adding she was transported by ambulance from the Leongatha Hospital to the Monash Medical Centre in Melbourne on 31 July.

Contrary to initial reports from police, who said Ms Patterson's children were present but did not eat the meal, the children had actually gone to the cinema.

They ate some of the leftovers the next day - but not the mushrooms which were scraped off because they don't like them.

She said the mushrooms used to prepare the meal were a mixture of button mushrooms purchased at a supermarket, and dried mushrooms purchased at an Asian grocery store in Melbourne several months ago, which were in a hand-labelled packet.

Mrs Patterson also admitted lying to investigators about a food dehydrator she had dumped at a local tip which they seized as part of their enquiries.

She said her estranged husband intended to join the lunch, but told her a day earlier he would not be attending.

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Mrs Patterson said she was voluntarily providing a statement because she believed it was a mistake to have initially provided a "no comment" interview to police based on a lawyer's advice who no longer represented her.

Police have said the investigation is likely to be lengthy due to the complexity of the case.

Detective Dean Thomas said last week: "We presume at this stage it was mushrooms but it's a complex investigation that I think will take some time."