LONDON — Migrants streaming into Europe have braved fierce storms, navigated turbulent waters, faced down police batons, water cannons and tear gas in Hungary, and stepped through fields in Croatia strewn with land mines.

Now some of the asylum seekers headed toward Western and Central Europe face another worry: toxic mushrooms.

Hanover Medical School, an academic hospital in north-central Germany, warned this week that about 30 migrants had been sickened — some of them severely — after eating mushrooms commonly called death caps.

The hospital made and distributed posters in Arabic, Kurdish and other languages cautioning migrants to avoid the fungus, which is native to Europe and can cause fatal liver and kidney damage. On Thursday, similar cases of mushroom poisoning were reported in Münster, about 110 miles west of Hanover. A dozen patients remained hospitalized on Thursday, three in critical condition, Dr. Michael P. Manns, chairman of the department of gastroenterology, hepatology and endocrinology at Hanover Medical School, said in an email.

Desperate migrants traveling for days with little to eat may have resorted to foraging for food as they made their way across Europe, where they hope to find asylum.

“Do not collect mushrooms, if you are unfamiliar with edible growing mushrooms here,” the Hanover hospital warned in the poster. “A mushroom you regard from your homeland as a delicious edible mushroom could be deadly here although they look similar.”

The death cap (Amanita phalloides) resembles several varieties of edible mushrooms, making it particularly dangerous to people who are unfamiliar with the local terrain. The mushroom is found across much of Europe and in the United States, California in particular. And right now it is in the middle of its three-month growing season in Europe.

“Since this fungus has no repellent taste and the first symptoms occur only after several hours, the risk of getting sick form its consumption is extremely high,” the hospital said. It urged anyone who had eaten mushrooms and later experienced nausea, diarrhea or other symptoms to head to the nearest hospital.

The death cap is an invasive species in the United States. It typically poisons a few people a year in California, often immigrants from Southeast Asia who confuse it with paddy straw mushrooms from their homelands, according to Anne Pringle, a biologist at the University of Wisconsin, Madison, who studies toxic mushrooms.