The BBC reports:
For 30 years, during the rainy season, scores of villagers in Yunnan province have died suddenly of cardiac arrest.
Following a five-year investigation, researchers from the Chinese Centre for Disease Control and Prevention (CDC) in Beijing say they have the culprit.
The mushroom, know as Little White, belongs to the Trogia genus and has three toxic amino acids, experts say.
Researchers found that the deaths, known as Yunnan Sudden Death Syndrome, occurred almost always during rainy season (from June to August), and at an altitude of 1800-2400m (5900-7900ft).
See also a report from AP.