Poisonous death cap mushrooms claimed the lives of two people at a New Year's Eve party, the Sydney Morning Herald reported.

Two out of four people who ingested the mushrooms died at the Royal Prince Alfred Hospital, a spokesman confirmed with the Herald.

The four were taken to hospital after eating the mushrooms at a party in Canberra, health authorities said.

"One person is still receiving treatment, but two people have passed away," the hospital spokesman said without providing other details about the fatalities.

The fourth patient, a man, was discharged from Canberra Hospital yesterday, a spokeswoman told the Herald.

The Canberra Times reported that all were believed to be Chinese nationals, and believed to have belonged to the same family.

Mycologist Dr Brett Summerell, director of science at the Royal Botanic Gardens, says death cap mushrooms, also known as Amanita phalloides, are possibly the most toxic in Australia.

In a statement this afternoon, Sydney Local Health District said eating just one of the mushrooms can be fatal.

Director of Emergency at Canberra Hospital, Dr Michael Hall, said the patient discharged on Tuesday was fine, and would not have any long-term problems from the poisoning.

"We believe that he had a much smaller serve of a mushroom-prepared meal," he told the Herald.

Death cap mushrooms typically grow around Canberra and in southern NSW and are most often found at the bottom of oak trees. These species are filled with amatoxin, which can attack enzymes involved in producing DNA and may cause liver failure upon ingestion.

The Herald reported three people had died from eating death cap mushrooms in the past decade and there had been about 12 reported cases of poisoning.

In its recent report, the Canberra Times said the man still receiving treatment is believed to be awaiting a liver transplant at the RPA.