The California Poison Control System has identified 21 cases of amatoxin poisoning clustered in northern California, likely resulting from death cap mushrooms, the state's department of public health said. The poisoning resulted in severe liver damage in several people, including children, and at least one of the patients may need a liver transplant, the department said.

Death cap mushrooms can easily be mistaken for safe, edible mushrooms because of their similar taste, smell, and appearance. The confirmed cases happened between mid-November and early December, a rainy season in the region that creates ideal conditions for the deadly variety to grow, mostly near oaks and hardwood trees like pine trees, the California Department of Public Health (CDPH) said. Though the cases are mostly in the Monterey and San Francisco Bay area of Northern California, the risk is statewide, the department warned.

"Death cap mushrooms contain potentially deadly toxins that can lead to liver failure," Dr Erica Pan, CDPH Director and State Public Health Officer, said in a statement. "Because the death cap can easily be mistaken for edible safe mushrooms, we advise the public not to forage for wild mushrooms at all during this high-risk season." The death cap mushroom is never safe to eat, even if it is boiled, dried, frozen or cooked. Eating the deadly mushrooms can cause watery diarrhoea, nausea, vomiting, abdominal pain and dehydration within six to 24 hours - and although symptoms may initially wane, severe or fatal liver damage can still occur up to eight days later. "Only people with extensive training and experience should eat wild mushrooms that they have picked themselves," Dr Edward Moreno, County of Monterey Health Officer, said in a statement. (BBC/ California Department of Public Health)