LAKE ELSINORE - No evidence of a deadly amoeba was found in a Lake Elsinore woman who died suddenly in June 2006, authorities say.

The family of Nicole Hedberg recently began to suspect that the so-called brain-eating amoeba could have killed her as they continue to question how a seemingly healthy 25-year-old woman would collapse and then die just days later.

According to a Riverside County sheriff-coroner's autopsy certified Sept. 13, 2006, Hedberg died of acute liver failure caused by chronic acetaminophen toxicity, Deputy Herlinda Valenzuela, a department spokeswoman, said Friday.

But Hedberg's family questioned that as her cause of death after hearing about the amoeba, Naegleria fowleri, which enters through the nose and attacks the brain and has been cited as the killer of six people across the country this year.

Hedberg and her fiance had recently moved to Lake Elsinore from Redondo Beach and would sometimes swim or ride watercraft in the lake.

"We have no clue why a healthy 25-year-old woman would just up and die three months after moving there," Hedberg's sister, Dawn Loew, said by telephone Friday.

"The hospital never said anything about liver failure other than her organs were shutting down one by one because of brain swelling," Loew said.

Hedberg's brain swelling collapsed her brain stem, Loew said the family was told by doctors.

Doctors were unable to do a spinal tap, because of her weakened condition, a test that might have identified bacterial meningitis.

Hedberg died 10 days after she collapsed.

After learning of the amoeba, which lives naturally in organic sediment in warm lake water but can be deadly when inhaled, Loew said the family realized Hedberg had displayed the same symptoms before her death as those linked to the amoeba deaths. Those symptoms include a fever, headaches and a stiff neck.

The coroner's office did further tissue sampling but notified Loew on Wednesday that no sign of the amoeba was found, she said.

However, the coroner's office has agreed to send tissue samples to the California Department of Public Health to conduct more thorough testing.

Valenzuela said Friday that the samples have been delivered to the state agency. A spokeswoman for the Department of Public Health said she could not confirm they had arrived.

"We will check for the amoeba," spokeswoman Lea Brooks said.

"If we can be provided with tissue samples, we will be happy to test them," she said.

The state testing will be done at the viral and rickettsial disease laboratory in Richmond by the California Encephalitis Project in collaboration with the national Centers for Disease Control and Prevention, Brooks said.

Brooks said that, out of more than 3,500 cases referred to that project, none had the laboratory data consistent with the deadly amoeba.

According to the CDC, the amoeba killed 23 people in the U.S. from 1995 to 2004.

Loew said she doesn't want to comment further about the possibility the amoeba killed her sister until she hears the results from the state tests.

"There are still so many questions surrounding this whole thing and that's unfortunate," Loew said.

She said the family wonders why an independent review of the coroner's autopsy results by medical experts through the family's own law firm also questions the finding of liver failure.

There is also a question, Loew said, as to why the family is now hearing that Hedberg suffered from sepsis, a life-threatening illness that typically results from the body's immune system's attack on a bacterial infection.

"Every day, we're being told something new," Loew said, adding they were never before told about sepsis.

"It's all very frustrating," she said.

Contact staff writer John Hall at (951) 676-4315, Ext. 2628, or jhall@californian.com.