There's a warning to stay away from death cap mushrooms because recent wet weather seems to have spurred their growth.
Half a mushroom is estimated to contain enough toxin to kill an adult.
"Death cap mushrooms can easily be mistaken for edible mushrooms but they can be deadly," ACT chief health officer Dr Kerryn Coleman said.
"All parts of the mushroom are poisonous and cooking them does not make them safe to eat."
The health officer urged people not to touch the wild mushrooms with bare hands, and to keep children and animals away from them.
"If someone may have eaten a death cap mushroom, urgently seek medical attention at a hospital emergency department and take any remaining mushroom to the hospital for identification," she advised.
The severe ill effects of the mushrooms usually set in from six to 24 hours after eating them. Symptoms include pain, nausea, vomiting and diarrhoea.
"The chances of survival increase if treatment is started early," Dr Coleman said.
There have been four deaths and several poisonings in the ACT associated with death cap mushrooms since 2002.
In November, three people went to ACT hospitals after ingesting poisonous mushrooms, prompting health authorities to warn people then against eating wild mushrooms.
November was not the usual time of year for the mushroom but their growth may have been promoted by the rains.
Amanita phalloides - known as death cap mushrooms - were also spotted sprouting a year ago in the ACT, which is significantly earlier than usual, again, most likely due to wet weather and mild summer temperatures.
They often grow near established oak trees, and are found when there is warm, wet weather. In Canberra this usually occurs in autumn but there is no specific mushroom season. They are appearing earlier than usual this year.
"Canberrans should be aware that it is never safe to pick and eat wild mushrooms," Dr Coleman said.
In 2012 death cap mushrooms killed two Canberra residents who ate them at a dinner party on New Year's Eve and in 2014 they seriously poisoned four others.
Anyone who sees a death cap mushroom in a public area, can report it to Access Canberra on 13 22 81.
