Immigration officials have not made clear how they intend to deal with workers who are unable to prove their legal immigration status in the course of inspections, but they said there was no moratorium on deportations.

Executives at American Apparel were both relieved and dismayed after receiving the warning from the immigration agency of discrepancies in the hiring documents of about one-third of its Los Angeles work force. The company has 30 days to dispute the agency's claims and give immigrant employees time to prove that they are authorized to work in the United States, immigration officials said. If they cannot, the company must fire them, probably within two months.

But no criminal charges were lodged against the company and no workers have been arrested, American Apparel executives and immigration officials said.

The fines followed discussions over 18 months between federal officials and American Apparel, after immigration agents first inspected the company's files in January 2008, said Peter Schey, an immigration lawyer representing the company. Schey said a raid had been averted because the company cooperated with the audit and because immigration agents had not found any labor abuses.

"There is no evidence of any exploitation of workers or violation of labor laws," he said. "And there is not a single allegation that the company knowingly hired an undocumented worker."

American Apparel and its outspoken chief executive, Dov Charney, have waged a campaign, emblazoned on T-shirts sold across the country, criticizing the immigration crackdown of recent years and calling on Congress to "Legalize L.A." by granting legal status to illegal immigrants.

Most garment workers in American Apparel's huge Los Angeles shop work directly for the company, not for subcontractors, its records show. They earn at least $10 to $12 an hour, well above minimum wage, and receive health benefits.

At a news conference last year, Mayor Antonio R. Villaraigosa of Los Angeles publicly lauded Charney for helping the city with its faltering economy by providing "the dream of a steady paycheck and good benefits for countless workers."

While it has been no secret that American Apparel's largely Latino work force probably included many illegal immigrants, Schey said the company had been careful to meet legal hiring requirements. Many illegal immigrants use convincingly forged Social Security cards or other fake documents when seeking work.

In a statement, Charney said that many of his workers cited by the immigration agency were "responsible, hard-working employees" who had been with the company for more than a decade. Charney, an immigrant from Canada, said he hoped they would be able to prove their legal status. But because of the recession, the company said, it would not be hurt financially if it had to replace them.