ACT chief health officer Dr Paul Kelly said death cap mushrooms could be lethal if ingested, with as little as five grams enough to kill an adult.

“It is crucial for people to understand that all parts of the mushroom are poisonous and cooking them does not make them safe to eat,” Dr Kelly said.

Death cap mushrooms are known to grow in the ACT. They often grow near established oak trees and can be found when there is wet weather.

Four people have died in the territory since 2002 after eating the deadly mushrooms, including two who ate them as part of a New Year's Eve dinner in 2012.

There have also been a number of poisonings, with the most recent serious cases coming in 2014, when four people were hospitalised.

Death cap mushrooms are often confused with other wild mushrooms, with Dr Kelly saying Canberrans should steer clear of wild mushrooms entirely and instead buy them from a reputable supplier.

Dr Kelly warned people not to touch wild mushrooms with bare hands and to keep children and animals away from them.

“If you think you have eaten a death cap mushroom, seek urgent medical attention at a hospital emergency department and take any remaining mushroom to the hospital for identification,” he said.

“Symptoms of poisoning generally occur 6-24 hours or more after eating mushrooms, and include pains, nausea, vomiting and diarrhoea.

“The sooner treatment begins, the better the patient’s chances of survival.”

Anyone who finds a mushroom in a public area is asked to contact Access Canberra on 13 22 81.

More information about death cap mushrooms is available on the ACT Health website.