An Australian woman hosted her ex in-laws for lunch. Less than a week later, three of them died and police suspect poisonous mushrooms are to blame.

• A woman hosted a lunch for ex in-laws, and now, three have died.
• The woman, Erin Patterson, has denied wrongdoing, and police said the deaths are "unexplained."

An Australian woman hosted her former in-laws for lunch in late July. Less than a week later, three of them died, and police suspect poisonous mushrooms are to blame.

On July 29, Erin Patterson hosted her former parents-in-law — Gail and Don Patterson — and her former mother-in-law's sister and her husband — Heather and Ian Wilkinson — for lunch at her home in the southern Victorian town of Leongatha, CNN reported. Patterson's ex-husband, Simon Patterson, did not attend, but their two children were present, according to CNN.

The following day, all four of Patterson's ex-in-laws fell seriously ill and were taken to the hospital, Victoria Police said. The two women — Gail Patterson, 70, and her sister Heather Wilkinson, 66 — died on August 4. Gail's husband, Don Patterson, 70, died a day later.

The fourth guest, 68-year-old Ian Patterson, remains in critical condition in the hospital.

Since the deaths, Erin Patterson has denied any wrongdoing.

On Monday, the 48-year-old told reporters: "I'm devastated. I loved them. And I can't believe that this has happened, and I'm so sorry," CNN reported.

Victoria Police provided an update on the deaths on Monday, saying that they'd launched a homicide investigation into the incident and that Patterson was a suspect because she'd cooked the meals for the guests and hadn't presented with any symptoms.

The symptoms the guests had are consistent with the consumption of death cap mushrooms, Detective Inspector Dean Thomas said, which are highly poisonous and can induce violent stomach pains, nausea, vomiting, and diarrhea. They can also cause serious liver and kidney damage, according to BC Centre for Disease Control.

"We have to keep an open mind in relation to this. It could be very innocent," Thomas said. "But again, we just don't know at this point … four people turn up, and three of them pass away, with another one critical, so we have to work through this."

Thomas also said they'd executed a search warrant for Patterson's address and interviewed her on Saturday, adding that police believed Patterson and her two children had eaten a different meal than the four in-laws.

The BC Centre for Disease Control reported that its local drug and poison information center received an average of 200 calls per year related to wild mushroom exposures and reported 39 deaths from 2017 to 2021. If a person ingests a death cap mushroom, the agency advises immediately transporting them to the emergency room because early treatment is paramount.

In May 2023, NPR reported that a team of Chinese and Australian researchers may have found an antidote for death cap mushroom poisoning after conducting studies on mice. The study, shared in Nature Communications, found that ICG — also known as indocyanine green — "is an effective antidote" for treating ɑ-amanitin toxicity in mice.