By STEVEN GREENHOUSE

WASHINGTON, July 15 - The 48 immigrants thought they were attending mandatory safety training by the Occupational Safety and Health Administration. But it was not until they showed up to the meeting in Goldsboro, N.C., last week that they discovered they had been summoned for an altogether different reason.

Federal immigration officials had posted fliers telling immigrant workers for several subcontractors at Seymour Johnson Air Force Base in Goldsboro that they had to attend a safety meeting. There was no meeting, however; instead there was a sting operation in which immigration officials arrested 48 people on charges that they were illegal immigrants from Mexico, Honduras, El Salvador and Ukraine.

The action had one branch of the federal government speaking out against another. The United States Labor Department as well as North Carolina's Labor Department on Friday criticized the sting, suggesting that it would make immigrant workers distrust safety officials just when safety agencies across the nation are stepping up efforts to reduce the disproportionately high injury rate among Hispanic workers.

Pam Groover, a spokeswoman for the federal labor department , said, "This is not something we were involved in, and we do not condone the use of OSHA's name in this type of activity." The Occupational Safety and Health Administration is the branch of the federal Labor Department that sets and enforces standards for workplace safety. Dean Boyd, a spokesman for the federal Bureau of Immigration and Customs Enforcement, which carried out the sting, said it was part of a stepped-up effort to crack down on illegal immigrants working at chemical plants, nuclear plants and other sensitive facilities.

Defending the use of ruses, Mr. Boyd said: "The primary reason to use tactics like this in federal law enforcement is to get people in a location where they can be arrested without running all over the place. That helps ensure the safety of these immigrants, the agents, the air base and the community at large."

Mr. Boyd said that as far as he knew this was the first time that immigration officials had enticed immigrants by representing themselves as OSHA officials.

"We certainly understand OSHA's concerns about the use of their name," Mr. Boyd said. "We're putting in place procedures to ensure appropriate coordination."

Mr. Boyd said the immigration bureau also used a ruse to help gather 60 illegal immigrants who were arrested on May 20 at petrochemical plants in six states. He declined to discuss details, but he said immigration and prosecutors have long used subterfuges to bring in people for arrest.

"For many years we have used undercover techniques in drug investigations, arms investigations and money-laundering investigations," Mr. Boyd said.

Juan Santos, the spokesman for North Carolina labor commissioner, Cherie Killian Berry, a Republican, said he hoped such stings using the OSHA name would never happen again.

"We're not at all opposed to what the federal government is doing to fight illegal immigration," Mr. Santos said. "Our concern is that when you start stinging people using the name of safety officials, you undermine the trust relationships we work very hard to build to help promote safety with employers and employees."

Immigrant groups and labor groups said the sting sent the wrong message when the federal and state labor departments had undertaken programs to reduce workplace injuries for Hispanics. In 2001, Labor Secretary Elaine L. Chao announced an education and training effort to reduce fatalities among Hispanic workers after studies showed their fatality rate was 20 percent higher than those of white and black workers.

"We think it's an absolute outrage and danger for the immigration authorities to use this type of tactic," said Cecilia Munoz, vice president for policy at the National Council of La Raza, an advocacy group for Hispanics. "Our labor law system is completely complaint-driven, and our ability to keep the work force safe depends on workers being able to complain, and by masquerading as OSHA officials, immigration authorities will clearly discourage immigrant workers from coming forward. This won't affect just immigrant workers, it will affect the safety of all workers."

Joe Hansen, president of the United Food and Commercial Workers Union, which represents more than 100,000 Hispanic workers, said, "The word being brought back to worksites after a scam like this is that OSHA can't be trusted. That kind of perception diminishes OSHA's ability to do the critical work of protecting America's labor force."

Felipe Bravo, a 47-year-old immigrant from Mexico City, was arrested at the meeting at the Air Force base, but was released when he proved that he was an American citizen. But he said his brother, Domingo, was arrested and faces deportation. They installed air conditioners and heating equipment, while many of the others worked in construction, lawn mowing or cleaning.

Mr. Bravo said that the government officials first served coffee and doughnuts and that one official stood up and said, "I got good news and bad news. The good news is we are not from OSHA, and the bad news is we're from the immigration office."

He said a swarm of immigration agents then entered the theater.

"It's not fair because they got my brother on false information, on having false papers, but they also used false information," Mr. Bravo said. "I agree with the government about trying to protect us against terrorism. That's good. But these people aren't terrorists. They came here to work."

Mr. Boyd said, "We believe it is a very serious vulnerability when there are illegal aliens working at Air Force bases, nuclear power plants, chemical plants and airports. They have access to some of the most sensitive work sites in the U.S. Our job is to take actions to immediately remove them from positions where they can do harm."