A man and a woman in their 60s died after eating poisonous mushrooms they picked in a forest, health officials in Toyohashi, Aichi Prefecture, said Saturday.
It is the first fatal case in Japan involving mushrooms known as "nise (false) kurohatsu" (Russula subnigricans) since 1996, the officials at the Toyohashi public health center said.
Experts and local authorities issued a warning urging people not to eat mushrooms found in the wild. In the autumn, large numbers of people enjoy picking mushrooms in forest areas.
According to the announcement, the two friends picked the mushrooms Wednesday in a forest in Toyohashi. They apparently thought that they were "kurohatsu" (Russula nigricans), which are not poisonous, the officials said.
The pair ate the mushrooms in miso soup later Wednesday, and in less than an hour started having difficulty breathing and other symptoms.
They were taken to a hospital, where the woman died Friday night and the man died early Saturday. Their deaths were caused by multiple organ failure, the officials said.
Nise kurohatsu is known as highly toxic, and consumption of a small amount can be deadly, they said.
The mushroom grows among evergreen oak trees and Japanese chinquapin from summer to fall, with the cap growing to 5 cm to 12 cm in diameter.
While korohatsu changes into a blackish color if it is cut, nise kuromatsu turns red, according to the experts.
The city of Toyohashi is urging people entering forests to pick mushrooms to be accompanied by someone experienced in distinguishing between edible and poisonous varieties.
The city government also plans to publicize information about poisonous mushrooms.
"Some people mistakenly believe, for example, that mushrooms of plain color are not poisonous. Please do not trust such false information," said Sadamichi Kato, a researcher at a science museum in Horai, Aichi Prefecture.
