Five years after FBI administrators pledged to clean up their much-maligned evidence lab, officials are again facing questions over shoddy lab work -- this time involving more than 100 DNA tests.

A bureau spokesman says the Justice Department's Office of Inspector General, its internal investigative branch, is looking into how an FBI lab technician might have compromised DNA tests over a two-year span.

Officials at the National Criminal Defense Lawyers Association, which has been critical of the lab, said they were unaware of the latest problem and urged the FBI to reveal more information.

"Our concern is just the typical Justice Department stonewalling on this thing," said Dan Dodson, an association spokesman. "Every defense attorney in every case should be notified."

Dr. Frederic Whitehurst, the former FBI lab chemist whose allegations of incompetence sparked the 1997 investigation, said the technician's mistakes are more proof that the lab should be subject to independent regulation and inspection.