Two residents of an elderly care home in California died and four other people were hospitalized after eating soup containing poisonous wild mushrooms picked by a caregiver, the Sacramento Bee reported.

Placer County sheriff's Lt. Mark Reed said the incident, reported Friday morning at the Gold Age Villa in Loomis, was believed to be an accident, the Bee reported. Reed said the dead were identified as Barbara Lopes, 86, and Teresa Olesniewicz, 73. The caregiver was among the four who were hospitalized, the Bee report said.

The Bee said the type of mushroom was not known.

However, Dr. Todd Mitchell, a Santa Cruz, Calif., doctor who is investigating an antidote to toxic mushroom poisoning, told NBC News that he is consulting on treatment of one of the patients sickened by amatoxin poison. A common cause of that poisoning is the Amanita phalloides -- death cap -- mushroom, which produces amatoxins that shut down liver function. 

The woman, who is in her 90s, is being treated with the so-called "Santa Cruz protocol" that includes use of the investigational drug Legalon, an intravenous form of silibinin, which is the extract of seeds from the milk-thistle plant. 

The treatment started Friday night, so it's still too early to tell how the woman, who was not identified, will fare, Mitchell said. However, dozens of patients treated with the milk-thistle drug and a protocol that emphasizes aggressive hydration typically have improved within 48 hours, he said. 

Nearly 6,000 people reported contact with suspicious mushrooms in 2010, and more than 1,300 people got sick, according to latest figures from the American Association of Poison Control Centers. Some 500 people suffered moderate to major injuries and at least one person died.

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