One of the three Canberrans being treated after eating the mushrooms was taken to Sydney's Royal Prince Alfred Hospital on Sunday, and two other people remain in a stable condition in Canberra.

ACT Chief Health Officer Paul Kelly said on Sunday evening that investigations by ACT Policing and ACT Health found no evidence the mushrooms were sold at the Dickson supermarket, as reported by the victims.

Previous deaths from the poisonous fungi have been linked to mushrooms collected in parks and gardens.

"Our investigations are still ongoing as to the source of the death cap mushrooms, however this remains an isolated incident and there have been no other recent reports of death cap mushroom poisoning in the ACT," Dr Kelly said.

"Two of the patients remain in a stable condition in ACT hospitals and one patient is currently receiving care at Royal Prince Alfred Hospital, Sydney. ACT Health is seeking co-operation in respecting the privacy of these patients during this time."

ACT Health reported the possible poisoning on Saturday and said the victims claimed the mushrooms were purchased from the Woolworths supermarket at Dickson about April 17.

No details of the victims have been released, except that the three live in the same household and presented to Calvary Hospital over a 48-hour period with similar symptoms.

Their ages, gender, suburb of residence and ethnicity have all been withheld to protect their privacy.

On Sunday, a Woolworths spokesperson confirmed the company was working with ACT Health but said no other incidents had been reported.

The Dickson store had mushrooms on sale and no information was posted for customers on Sunday.

"We’d like to acknowledge the swift action taken by Woolworths in response to the initial information about the source of the mushrooms," Dr Kelly said.

Just one death cap mushroom contains enough poison to kill an adult.

Symptoms of death cap mushroom poisoning include stomach aches, nausea, vomiting and diarrhoea, and generally appear six to 24 hours after ingesting the mushrooms.

There have been four fatalities and 12 reported incidents of poisoning associated with death cap mushrooms in the ACT.

Two Canberrans died and a third was treated in hospital in January 2012 after eaating the toxic mushrooms.

Incidents dating back to the 1990s have caused health authorities to issue strong warnings about the dangers of picking and eating wild mushrooms in Canberra.