The Agriculture Department's inspector general has significantly expanded its probe into the agency's handling of mad cow disease, agreeing to examine the USDA's unannounced decision last year to relax restrictions on trade in Canadian beef.

In response to a request by Sen. Thomas A. Daschle (D-S.D.), inspector general Phyllis K. Fong said in a letter this week that her office will look into the agency's "actions pertaining to the importation of Canadian beef products," and whether it properly enforced measures to reduce the risk of mad cow disease from Canadian beef.

The new inquiry is the fourth initiated by the inspector general regarding mad cow disease. The agency's independent watchdog office was already investigating allegations that USDA officials falsified records regarding the diseased animals, as well as questions about the agency's surveillance program before and after the discovery of an infected cow in Washington state and concerns that it failed to properly test an apparently ill 12-year-old Texas animal.

The newest probe will involve auditors and investigators but is not considered a criminal inquiry, said counsel to the inspector general, David Gray. He said the inspector general's office will interview agency officials and review records to see whether administrative procedures were followed.

Several Democratic senators asked for an inquiry in May after the Agriculture Department acknowledged that it had quietly expanded a program last fall that allowed only certain kinds of Canadian beef to be imported into the United States.

Department officials later admitted they had not properly notified the public, the industry or Congress about the changes, which were announced on a difficult-to-find page of a department Web site. Some of the changes implemented by the Agriculture Department were also being debated in a formal rulemaking process.

Daschle and several other senators requested the new investigation last week after information emerged that the department may have also quietly lifted several safety requirements in place to protect against mad cow contamination from Canada.

"Unfortunately, in recent months the American public has been getting more and more troubling information about USDA's actions regarding beef imports," Daschle said. "I'm hopeful the inspector general's investigation will result in a truly comprehensive look at USDA's handling of imports from Canada in the wake of the discovery of mad cow disease."

Beth Johnson, special adviser to Agriculture Secretary Ann M. Veneman, said yesterday that the agency welcomes the review and looks forward to recommendations on how to improve its procedures. She also said that whatever problems may have existed with the Canadian beef import permits, they did not jeopardize public health.

"This is not a problem of food safety but of process, of not putting the information out to the public to let them know about the changes that occurred," she said.

Also yesterday, the Agriculture Department said that for the second time this week, an animal suspected of having mad cow disease turned out, with further testing, to be free of the virus. The agency began a more aggressive mad cow disease surveillance program last month, using a test known to produce false positives.

The first North American case of mad cow disease was discovered in Alberta, Canada, in May 2003, and the United States stopped all Canadian beef imports. In August 2003, Veneman announced a loosening of the ban to allow certain cuts of "low risk" Canadian beef to be brought into the United States.

In the next several months, Agriculture officials acknowledge, they further loosened the ban to allow in other Canadian beef products, including some ground beef and sausage considered to have a higher risk of mad cow contamination.

The fact that Canadian processed and ground beef was entering the United States came to light during federal court proceedings in Montana, where the rancher association R-CALF USA filed a lawsuit against an Agriculture Department proposal to expand the cross-border beef trade. A federal district court judge ruled in May that the department had not followed required procedures when it relaxed its ban on Canadian beef, and the judge issued a preliminary injunction to endimportation.

R-CALF then collected public statistics that it said indicated 33 million pounds of Canadian beef banned under the August 2003 guidelines had been permitted to enter the United States. The Agriculture Department did its own analysis and concluded that 2.2 million pounds of Canadian beef came in under permits it had improperly issued.

Gary Weber, director of regulatory affairs for the National Cattlemen's Beef Association, said the inspector general's review was necessary. "This shouldn't be considered a public health risk," he said, "but administrative procedures may not have been followed, and that should not have occurred."

But Bill Bullard of R-CALF said public safety may have been compromised by some of the changes allowed by USDA, which he said ignored accepted scientific guidelines on how to protect against the spread of mad cow disease.

The USDA began an aggressive mad cow disease surveillance program last month, after a cow in Washington state tested positive for the disease.Sen. Thomas A. Daschle (D-S.D.) and other senators requested the new inquiry on Canadian beef.