LAKE ELSINORE - The state heath department has determined that no evidence of a so-called brain-eating amoeba was found in tissue samples from a Lake Elsinore woman who died suddenly last year.

Nicole Hedberg, 25, collapsed in June 2006, and then died a few days later. A Riverside County coroner's autopsy concluded the cause of her death was acute liver failure caused by chronic acetaminophen toxicity.

But after hearing about the amoeba, and relating its symptoms to those Hedberg had before she died, family members started to suspect it might have had something to do with her death.

Riverside County forensic pathologist Scott McCormick stated in a microscopic examination report that no organisms were found in Hedberg's brain, nor was there any brain inflammation.

However, county coroner's officials agreed to send some of Hedberg's tissue samples to the California Department of Public Health, which is able to test more thoroughly for the amoeba, Naegleria fowleri, which enters through the nose and attacks the brain.

Family members of Hedberg have said that she and her fiance had recently moved to Lake Elsinore and would sometimes swim or ride watercraft in the lake.

Lea Brooks, a spokeswoman for the state agency, said Monday that tests for the amoeba proved negative. The tests were 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, she said.

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

She said Monday that the tissue sample was not good enough in quality to test for encephalitis, which is an inflammation of the brain.

It is believed that the Centers for Disease Control and Prevention also may have conducted tests for the amoeba from Hedberg's tissue samples, but a spokeswoman there said the agency was not allowed to comment on medical results.

Another spokesperson with the California Department of Public Health previously said the CDC test results showed no evidence of the amoeba.

Members of Hedberg's family who have previously spoken about her death and subsequent tests did not return calls and e-mails requesting comment.

According to the CDC, the amoeba killed 23 people in the United States from 1995 to 2004.

There were reports of six people across the country dying this year from the amoeba, which lives naturally in organic sediment in warm lake water but can be deadly when inhaled.

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