Nov. 28, 2012 -- Another elderly person has died from accidental mushroom poisoning at a California senior care facility, bringing the death toll to four.

The latest victim, 92-year-old Dorothy Mary Hart, died at a nursing home, according to The Associated Press. The date of her death has yet to be released.

The first two women died the day after a caregiver at their senior-care facility inadvertently served them a meal with poisonous mushrooms picked on the Loomis, Calif., property Nov. 8. The caregiver and three other residents of Gold Age Villa were hospitalized, according to WTEN-TV, the ABC News affiliate in Sacramento.

Hart was among those to be hospitalized after the poisoning, but she was released and living in a nursing home.

Teresa Olesniewicz, 73, died the morning of Nov. 9 and Barbara Lopes, 86, died that night, according to the county coroner. Frank Warren Blodget, 90, the third victim, died Nov. 17.

"It looks like a tragic accident," Lt. Mark Reed of the Placer County Sheriff's Department said.

Reed told the Sacramento Bee that the caregiver "just didn't know" the mushrooms were poisonous. It is not clear what kind of mushroom the victims ate, however.

Dr. Pierre Gholam, a liver specialist at University Hospitals in Cleveland, said he has seen an uptick in wild mushroom poisonings in his area, too. More than two dozen patients have arrived in the past three years with telltale mushroom poisoning symptoms, he said, including diarrhea followed by kidney and liver failure.

Gholam, speaking to ABC News by phone from a meeting of the American Association for the Study of Liver Diseases in Boston earlier this month, said doctors there from across the country report similar increases in mushroom poisoning patients, even in areas not typically known for mushroom poisonings, such as the Midwest.

Specialists historically see case clusters in Northern California and in the Northeast.

"Clearly, there is something that has changed, in my mind, that has led to more mushroom poisoning cases," he said. "It looks like a nationwide phenomenon."

The reasons are unclear but Gholam suggested that more people could be picking their own mushrooms in the bad economy to save money.

Gholam's hospital is one of only a few authorized by the federal government to give patients an antidote called silibinin, which blocks the poison from attacking the liver. Fourteen patients have come from up to 150 miles away for the life-saving drug.

The poison in these mushrooms is called amatoxin, and it's colorless and odorless, so people who pick or eat them won't know until it's too late, Gholam said. The poison fungi can also come in different sizes and shapes. Cooking or freezing the mushrooms does not deactivate the toxin.

Typically, people begin to feel sick within six hours of eating the mushrooms, and come down with severe diarrhea, which causes dehydration and kidney failure, he said. Without the antidote, liver failure can set in after 72 hours, and the needs a liver transplant after 96 hours.

"I think at this point, it is absolutely critical to spread the word -- especially to folks that picked mushrooms -- that the landscape has changed," Gholam said.