A federal judge dealt a legal setback to the Agriculture Department's tough new meat safety regulations today, blocking the department from effectively shutting down a Texas processing plant where ground beef allegedly was found to contain unacceptable levels of salmonella in repeated tests this year.

In a ruling that food safety groups said could inhibit the department from enforcing the new regulations in other plants across the country, the judge allowed Supreme Beef Processing of Dallas to continue churning out 500,000 to 600,000 pounds of ground beef a day while it fights the department's effort to stop the production--a legal battle that could have major implications for the meat processing industry.

At stake in the case is more than just one company's future. In suing the department, Supreme Beef argued that federal officials went beyond their statutory power in setting tough new limits on permissible levels of salmonella in raw beef and poultry, rules that apply to more than 3,000 processing plants nationwide. In siding with Supreme Beef today, U.S. District Judge A. Joe Fish said it was an "open question" whether the department had exceeded its authority in issuing the rules.

Congress, in passing the Meat Inspection Act of 1907, gave Agriculture Department officials the authority to issue and enforce food safety regulations. The department contends that its new salmonella rules fall within that mandate. But the company said Congress did not intend to give the department the authority to issue such aggressive rules. In its lawsuit, the company noted that "because salmonella is destroyed during normal cooking, the presence of salmonella is not a public safety issue" with which the department should be concerned.

"We strongly disagree" with the company's arguments "and we're going to do whatever it takes to pursue this matter fully," said Andy Solomon, a spokesman for Agriculture Secretary Dan Glickman.

Salmonella is a bacterium that kills an estimated 550 people and causes 1.4 million illnesses a year in the United States.

The company is the first in the nation to fail to meet the department's standards since the new regulations began being phased in almost two years ago, lawyers in the case said. For that reason, both sides view the lawsuit as a test of the department's legal authority to implement the new limits.

Until agriculture inspectors moved against the company last month, Supreme Beef was one of the biggest suppliers of ground beef to the federal school lunch program, also overseen by the Agriculture Department. But the department has canceled the company's contract.

Fish granted Supreme Beef's request for a preliminary injunction, allowing it to continue producing ground beef until the dispute is settled at a trial months from now. The company, which also produces ground poultry, said ground beef is the biggest part of its business and that halting production would force the plant to close.

A coalition of food safety groups immediately criticized the decision as a potential obstacle to the department's effort to replace old methods of inspection, involving "sight, feel and smell," with new scientific tests for microscopic contaminants such as salmonella.

"This is a very significant setback for the government," said Caroline Smith DeWaal, director of food safety at the Center for Science in the Public Interest, an advocacy group. "The industry not only has been meeting these standards, they've been beating them. They're passing with flying colors. And this one company should not be allowed to bring that system down."

Although Fish's ruling applies only to Supreme Beef--allowing it to continue operating free of the standards until the lawsuit is resolved--DeWaal and others said they worry that the department will be hesitant to enforce the regulations elsewhere while the case in Dallas is pending.

The rules are part of an Agriculture Department initiative called Hazard Analysis Critical Control Points. It requires processing companies to identify points in their production systems at which raw meat and poultry are vulnerable to pathogens such as salmonella and take steps to prevent contamination.

Besides contesting the department's authority to implement the new rules, Supreme Beef's lawyer, John Gilliam, also disputed the test results, saying the company's ground beef was "in compliance with these standards, as bad and inequitable as they are."