Chipotle Mexican Grill said on Thursday that it had fired a substantial number of the 1,200 employees at its 50 Minnesota restaurants after a federal immigration audit found some were illegal workers.

The circumstances of the firings, which began in early December, sparked a protest by several dozen people around noon on Thursday at a downtown Minneapolis Chipotle restaurant. Minneapolis police arrested eight participants after they chained themselves together inside the restaurant. They were cited for trespassing.

Denver-based Chipotle would not disclose how many Minnesota workers were fired. Protesters said the number was 700. The U.S. Immigration and Customs Enforcement (ICE) office, which conducted the Chipotle worker audit, declined to comment. However, a source said the number of Minnesota employees fired was closer to 350. Chipotle has apparently replaced the terminated employees. Its Minnesota employment was 1,200 both before and after the firings, said spokesman Chris Arnold.

The protesters didn't claim that all the fired employees were legal U.S. workers, but they did assert that the workers were fired without much explanation and without being given time to provide documents proving they were legal U.S. workers. They also claimed that fired workers had to endure delays in being paid. The claims, if true, would appear to be violations of Minnesota's labor laws.

Chipotle responded that accused workers were given one-on-one opportunities to provide documents that could prove they were legally able to work in the United States. If they couldn't, they were fired in accordance with U.S. law, Arnold said, adding that pay and accumulated vacation time were paid promptly.

The investigation of Chipotle began several months ago, Arnold said, when ICE asked to see work eligibility documents. The company was not told why it was singled out for review. ICE then provided Chipotle with a list of employees whose documents might be invalid, he said.

Chipotle tries to screen new employees, but some provide false documents showing they are eligible workers, Arnold said. In cases where employees insist they have the proper documents, Chipotle has sought to give them extra time to produce the identification, he said.

"We have asked ICE whether they would allow a 90-day period to resolve discrepancies, and they have told us that they absolutely would not," Arnold said.

One of the protest organizers, Greg Nammacher, secretary-treasurer of the Service Employees International Union (SEIU), Local 26 in St. Paul, said the purpose of the demonstration was "to send a message to corporations that they can't sell Mexican culture and Mexican food and sell out Mexican workers." None of the Chipotle workers are represented by his union.

Although Nammacher said it was one of the largest immigration-related dismissals in his experience, about 1,250 janitors in the Twin Cities lost their jobs in November 2009 after federal officials challenged their immigration status.

A meeting was held two weeks ago between Chipotle and SEIU and others representing fired workers. Both sides said no agreement was reached.

Nammacher said that while Chipotle is not allowed to employ illegal workers, the workers deserved more humane treatment than they received.

"Companies all over this country are using immigrant labor, and then, when the government shines a light on those employees, the companies wash their hands of them," Nammacher said. He added that he was not accusing Chipotle or other companies of deliberately employing illegal workers.

Some of the employees participating in Thursday's protest said they'd had a long tenure with Chipotle.

Maria Cortez of Minneapolis said she has lived in Minnesota 14 years and spent the past six working at a Chipotle restaurant near Lake Calhoun. One day in early December, she and 12 other workers were fired as part of the first wave of terminations. Cortez was told she lacked the legal status to work there, but was not given a chance to show her Minnesota driver's license. (Federal rules say a driver's license alone is not sufficient proof of legal status.)

Juan Peres of Minneapolis said he was fired after working for five years at the Lake Calhoun restaurant. But he declined to say whether he was a legal worker, citing an ongoing investigation of him.

Steve Alexander • 612-673-4553