ATHENS, Ga. - At least three researchers have been exposed to a potentially fatal parasite in University of Georgia laboratories since 2000.

None of the researchers tested positive for Trypanosoma cruzi, a microscopic parasite found in parts of Central and South America, and UGA's existing labs pose no threat to the public, according to UGA administrators - but they are not releasing any records on safety lapses at the university's bioresearch labs.

The university denied a September open records request by a Texas-based nonprofit seeking records of exposure to biological agents or safety failures since 2000. UGA cited an exemption for medical records under Georgia's Open Records law.

UGA released just one document: a protocol for reporting exposure to T. cruzi and filing a worker's compensation claim.

The lack of documentation is suspicious because universities typically keep thousands of pages of such records, said Edward Hammond, the U.S. director of the Sunshine Project, a group that advocates citizen oversight.

"If the University of Georgia has an effective bio-safety program, it's not credible that they wouldn't have more paperwork," Mr. Hammond said.

"Humans are fallible. Equipment breaks. It's basically like saying 'Our researchers are perfect. We don't make mistakes,'" he said.

But that's exactly the case, according to David Lee, UGA's vice president for research.

"Because we haven't had accidents doesn't mean we're hiding something," he said. He said the three researchers accidently pricked themselves with T. cruzi needles.

T. cruzi causes Chagas' disease, a usually mild illness transmitted by blood-sucking insects that causes fever and skin lesions but can lead to fatal heart problems and malformed intestines if untreated for years. The exposures came in Bio-Safety Level 2 labs.