A federal investigator has found sparse government scrutiny of the safety of drug trials involving millions of people, saying inspectors are few and their findings are rarely followed up, a newspaper reported Friday.

A report due to be released Friday finds that the federal Food and Drug Administration audited less than 1 percent of testing sites, The New York Times reported. The agency has just 200 inspectors to monitor an estimated 350,000 test sites.

When inspectors do flag serious problems, their findings are frequently downgraded by senior officials and almost never followed by inspections to see whether the issues have been resolved, according to the newspaper, which cited the report by Health and Human Services Department inspector general Daniel R. Levinson.

The FDA found serious problems at test sites 348 times between 2000 and 2005. But only 26 investigators were disqualified from conducting further clinical trials, and data was disqualified just twice, The Times reported.

The FDA's chief medical officer, Dr. Janet Woodcock, said the agency was "working to address these problems very aggressively."

Meanwhile, President Bush signed a bill into law Thursday that is intended to boost the FDA's power to police prescription drug safety. It devotes more focus to drugs already on the market, as opposed to those awaiting approval, and gives the agency more authority to act when problems emerge.

The FDA oversees the safety of companies' drug or medical device trials, while the Office for Human Research Protections does the same for federally financed tests. There is no federal monitoring of privately financed, noncommercial trials.