SYDNEY — An Australian woman has been charged with murder over the suspected mushroom poisoning deaths of three people.

Erin Patterson was arrested on Thursday morning and police have spent the day searching her home east of Melbourne.

Ms Patterson, 49, had served the family lunch after which the trio, who included her former in-laws, fell ill. A fourth person survived.

Toxicology reports suggest the victims consumed deathcap mushrooms. Ms Patterson maintains she is innocent.

She has said she did not intentionally poison her guests at the lunch in the Victorian town of Leongatha on 29 July.

Her former husband Simon Patterson had also been invited to the family lunch, but was unable to make it at the last minute.

Erin Patterson was named as a suspect by police after she and her two children appeared unharmed after the lunch.

Police in the state of Victoria took Ms Patterson into custody on Thursday.

Homicide squad Inspector Dean Thomas stressed the complexity of the case in a press conference, describing it as a tragedy that may "reverberate for years to come".

"I cannot think of another investigation that has generated this level of media and public interest, not only here in Victoria, but also nationally and internationally," he added.

Gail and Don Patterson — the parents of Ms Patterson's ex-husband — were guests at the lunch along with Gail Patterson's sister Heather Wilkinson and brother-in-law Ian Wilkinson.

The four were taken to hospital on 30 July reporting violent illness, police say.

Within days the Patterson couple, both 70, and Ms Wilkinson, 66, had died. Wilkinson, 68, was taken to hospital in a critical condition but later recovered after two months of treatment.

Erin Patterson has said she herself was taken to hospital after the meal due to stomach pains, and was put on a saline drip and given medication to guard against liver damage.

She has said she served a beef wellington pie using a mixture of button mushrooms bought from a supermarket, and dried mushrooms purchased at an Asian grocery months earlier.

"I am now devastated to think that these mushrooms may have contributed to the illness suffered by my loved ones," she wrote in a statement in August.

"I really want to repeat that I had absolutely no reason to hurt these people, whom I loved."

Her children, who were not present at the lunch, ate some of the leftover beef Wellington the next day. However the mushrooms had been scraped off the dish as they do not like the fungi, she said. — BBC