The ACT Health Directorate says the food was for a private meal and no food containing the poisonous mushrooms was given to any member of the public.
In a statement, the authority said the premises in Canberra have been inspected and there is no risk of exposure to the public.
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A 52-year-old woman died and a 38-year-old woman died in hospital in Sydney on Wednesday after eating the meal.
A 51-year-old man remains in a critical but stable condition at the Royal Prince Alfred Hospital in Sydney.
ACT Health said a fourth person who was initially treated for mushroom poisoning in Sydney was not part of the group.
It said there were four people at the meal in Canberra, but one of them did not eat the mushrooms and remains well.
