She invited four people over for lunch. A week later, three were dead.

Australia is gripped by the mysterious deaths of three people in a suspected poisoning case that reads like a fictional thriller.

Two couples were invited to lunch at a palatial country home in the state of Victoria one Saturday in late July. They included a local pastor and his wife. All four were known to locals as pillars of the tightknit rural community.

That night, they all became seriously ill with what appeared to be food poisoning. A week later, three of the four were dead. One man remains in a hospital in critical condition, awaiting a liver transplant. The host of the gathering - a woman in her 40s - and her two children were unharmed.

Police suspect the victims ate death cap, or Amanita phalloides, mushrooms, one of the deadliest known mushrooms to humans. But whether the poisonings were intentional, or if the fungus is even the culprit, is shrouded in mystery. The guests’ symptoms were consistent with mushroom poisoning, medical experts and investigators say.

Homicide detectives have searched the home of Erin Patterson, the 48-year-old woman who hosted the gathering in Leongatha, about 70 miles from Melbourne. She was taken in for questioning Saturday and released without charge later that evening.

During the search, investigators seized several items they say are of interest to the case. A food dehydrator found at a local landfill is apparently also being tested to see if there is any link, Melbourne’s Age newspaper reported, citing an anonymous police source close to the investigation. Police declined to confirm whether a dehydrator is among the items being examined.

“It’s a complex investigation,” Detective Inspector Dean Thomas, head of the Victorian police homicide squad, said at a news conference. “At this point in time the deaths are unexplained.”

Thomas said the host is a suspect “because she cooked those meals for the people.” But he added, “we have to keep an open mind in relation to this that it could be very innocent.”

Death caps - which taste delicious according to people who have mistakenly eaten them, and survived - look similar to other nonpoisonous mushroom species. That makes them easily mistakable to people who forage for them in the wild. Just half a cap can cause liver damage. A possible antidote is available in Europe, but is awaiting approval in the United States and elsewhere.

Approached by reporters outside her Leongatha home this week, Patterson said she’d made the meal for “the best people I’ve ever met” and was devastated by their deaths. “I just can’t fathom what has happened.”

She declined to say what was on the ill-fated lunch menu, or whether she had eaten it. Police say her children were given a different meal than the adults.

Police have not named those who died, but according to local media reports, they were the host’s parents-in-law, Gail and Don Patterson, both aged 70, and Heather Wilkinson, 66. Ian Wilkinson, 68, remains in hospital.

“I can’t believe that this has happened and I am so sorry that they have lost their lives,” a tearful Patterson told reporters. “I didn’t do anything, I loved them, and I’m devastated that they’re gone.”

If the link to mushrooms is confirmed, it would not be the first time death caps have caused serious injury to multiple victims, including members of the same household.

In the fall of 2016, during an unusually large bloom in the San Francisco Bay Area, three people required liver transplants after eating the deadly mushrooms. Several members of one household - including an 18-month-old girl - became seriously ill after eating grilled death caps given to them by someone who had apparently picked them in the mountains earlier that day. The toddler, who required a liver transplant, now has permanent neurological damage. She ate half a cap, according to a federal report.

Experts say death caps initially result in gastrointestinal problems, vomiting and diarrhea. In severe cases, the toxins in the mushrooms can cause kidney and liver damage.

The Centers for Disease Control and Prevention estimates that the deadly mushroom is responsible for 90 percent of fatal fungi ingestions worldwide.

In a potential twist in the Australia case that was seized on by local media, the lunch party host’s estranged husband, Simon Patterson, nearly died last year from what he described as “serious gut problems.” In a Facebook post at the time, he said he collapsed at home and spent 16 days in an induced coma, undergoing several operations, mostly on his small intestine. He couldn’t immediately be reached for comment.

Police confirmed the couple had separated, but described their relationship as “amicable.”

The Leongatha deaths have rocked the local community. A hub for dairy farms that dot the lush Gippsland countryside, the town has fewer than 6,000 residents. Korumburra, the nearby town where the victims lived, has a population of about 4,700.

Wilkinson, the pastor, was well-known in the town, and parishioners of Korumburra Baptist Church gathered Tuesday to pray for his recovery.

“We are deeply bereaved by what has happened,” local parishioner Joyce Fleming told Nine News.

“I don’t think there’d be any person in this town who wouldn’t be feeling grief at the moment,” said local resident Leigh Spaull, whose children were taught by one of the victims.