Two residents of an elderly care center are dead and four people are in the hospital after a caregiver allegedly served soup made from poisonous wild mushrooms. The deceased victims are 86-year-old Barbara Lopes and 73-year-old Teresa Olesniewicz, who lived at the Gold Age Villa in Loomis, Calif., according to the Sacramento Bee. A caregiver reportedly foraged mushrooms on the grounds of the senior living center before using them in a meal. The poisonings are believed to be accidental, and the caregiver who allegedly prepared the soup is one of the people hospitalized, Sheriff's Lt. Mark Reed told the Associated Press. The three others hospitalized were elderly residents of the Gold Age Villa. The variety of poisonous mushrooms that were used in the soup is yet unknown, but Dr. Todd Mitchell, a Santa Cruz, Calif., doctor who is reportedly consulting on treatment of one of the patients, told NBC News that the patient is suffering from amatoxin poisoning. [10 Most Common Poisonous Plants] Multiple mushroom species in California contain the poison, which accounts for 90 percent of mushroom-related fatalities and leads to liver failure if untreated, according to a 2010 paper on amatoxin in the journal Toxicon. But the mushroom responsible for the most deaths, in California and worldwide, is Amanita phalloides, or the death cap. The non-native species bears a treacherous resemblance to a few edible varieties, but it packs a potentially fatal dose of amatoxin in as little as 1.1 ounces (30 grams), or roughly half a mushroom cap. The patient whose treatment Mitchell is consulting on is reportedly being treated with intravenous silibin, an experimental drug derived from milk thistle seeds that hasn't yet been approved by the U.S. Food and Drug Administration. Last month, the drug, which is approved for use in Europe, apparently saved the life of a Connecticut woman who had consumed the destroying angel mushroom (Amanita bisporigera), a close cousin of the death cap (destroying angels are a native species in California). When other treatments didn't seem to be working, the hospital board approved emergency administering of the experimental drug, and the woman showed signs of improvement soon after, reported the Hartford Courant.