Victoria state police also charged the woman with five counts of attempted murder – two related to the meal on July 29 this year and three related to separate incidents in 2021 and 2022 when they said a 48-year-old man became ill following meals.

Police had earlier searched the woman’s house with the help of technology detector dogs trained to sniff out tiny electronic devices such as USBs and SIM cards, which are easy to hide.

The woman, who was not named by police, was remanded in custody and will appear in court on Friday.

“Today’s charges are just the next step in what has been an incredibly complex, methodical and thorough investigation by Homicide Squad detectives,” Dean Thomas, the detective in charge of the investigation, said in a statement.

Don Patterson, his wife, Gail, and her sister Heather Wilkinson became ill and later died after the lunch in Leongatha, a small rural town around 135 km (85 miles) southeast of Melbourne.

A fourth man, Wilkinson’s husband, Ian, a pastor in a nearby town, was released from hospital in September.

State broadcaster ABC reported the woman had told police she did not intend to poison her guests and had herself been hospitalised after the lunch.

The mysterious deaths have gripped Australia. Deaths from eating mushrooms are relatively rare in the country, which has several species, including the “death cap” mushroom, that are dangerous enough kill a human.

(Reporting by Renju Jose and Alasdair Pal in Sydney; Editing by Lincoln Feast and Gerry Doyle, William Maclean)