Federal investigators have uncovered widespread flaws and in some cases possible fraud in private testing laboratory results that form the data base for much of the government's chemical, drug and pesticide safety standards.

Information gathered by the Food and Drug Administration on test procedures by three private laboratories has been turned over to Justice Department officials in Chicago and New Jersey, according to federal officials. The investigations began last year.

Officials involved in the investigations by both the FDA and the Environmental Protection Agency said the faulty test results could cause problems in determining whether some products already approved for the marketplace are safe.

"Based on what we've found so far there is a serious question about the data generated by any private testing laboratory," and FDA official said yesterday. "We don't know what data is bad but at the same time we don't know what is good either."

Last month EPA announced it had found "deficiencies" in tests performed for pesticide firms by Industrial Biotest Laboratory of Northbrook, Ill. The suburban Chicago laboratory ran 3,400 pesticide tests and has done other types of testing for a wide variety of manufacturers dealing with federal agencies such as FDA and the National Cancer Institute.

Federal officials who declined to be identified, said virtually every major or "pivotal" study done by IBT has shown serious flaws. The laboratory is one of the firms referred to the Chicago U.S. attorney's office for further investigation based on the FDA's investigation.

EPA officials said they have found at lest four other testing laboratories with suspect testing results. The four firms, officials said, have conducted a total of 4,000 animal tests for pesticide firms which in turn were used by EPA to set safety standards.

"We're looking at IBT as just the tip of the iceberg," said Edwin L. Johnson, EPA's pesticides chief. "There is no indication that the rest of the industry runs its business any differently that IBT does."

The other two firms identified as having been referred to Justice officials for further action are G. D. Searle & Co., a leading pharmaceutical manufacturer, and Biometric Testing Inc. of Englewood Cliffs, N.J.

IBT and Searle have denied manipulating test data. Bimetric could not be reached for comment.

The Searle firm was the subject of extensive hearings last year by the Senate Health and Administrative Practice and procedure subcommittees. At those hearings subcommittee Chairman Sen. Edward M. Kennedy (D-Mass.) sharply questioned the entire animal research industry. The hearings touched off the FDA's investigation into testing laboratories, FDA officials said.

Federal officials estimate that there are about 700 private testing laboratories scattered around the United States. Most do only a few animal studies on contract to commercial manufacturers. But some, such as IBT, offer a wide variety of testing services.

EPA officials said they are preparing a spot-check program of as many as 100 laboratories which do pesticide testing for commercial manufacturers. The agency has already notified 33 pesticide makers to review their own data supplied by IBT, and plans to call on as many as 100 more for similar in-house reviews.

The spot checks by the agency will be full-scale audits matching raw data complied by testing laboratories with the final reports they submit to manufacturers, EPA officials said.

Similar audits already run on some pesticide testing labs have turned up test animals which were reported to have died one week and then been alive the next officials said.

The officials said a large number of the pesticide products tested by lags which have turned up suspect results are used on crops grown for human consumption.

FDA officials appeared split over the seriousness of the laboratory data findings. One official, who asked not to be named, said the pattern of the test data deficiencies appeared "mind boggling."

Ernest Brisson, coordinator of the FDA's toxicological laboratory inspection program, however, said the FDA's findings so far were not overly disturbing. "We expected worse," Brison said.

In its first 40 laboratory examinations, Brisson said, FA investigators had to notify five firms of "serous deficiencies."

He acknowledged that the early inspections were superficial and were done by inexperienced inspectors. ""We're learning as we go along," he said.