According to a Wall Street Journal report, a researcher in the Federal Bureau of Investigation's cyber-protection unit got infected with the fast-spreading Internet virus that e-mailed private FBI documents to outsiders—all on the eve of a Senate hearing into troubles at the unit.

Although the Sircam virus didn't spread to other computers at the FBI's National Infrastructure Protection Center, it did send at least eight documents to a number of outsiders. One, about the investigation into an unrelated virus, was marked "official use only." The Sircam virus has infected thousands of computers since its discovery last week.

FBI spokeswoman Deb Weierman said that no sensitive or classified information about continuing investigations was disclosed Tuesday. The "official use" designation protects documents from disclosure under the US Freedom of Information Act.

Tuesday, at least three people said they received some of the FBI documents, including a 23-year-old Internet-security expert in Belgium, Niels Heinen. He operates a Web site that reports on Internet break-ins and speculated that the analyst, Vince Rowe, visited the site on the infected computer. Mr. Rowe didn't respond to a request for comment.