Washington ? Federal agents descended Thursday on global retail giant Wal-Mart and arrested some 300 illegal immigrants as they came off overnight cleaning shifts at stores in 21 states, and agents also hauled away boxes from the company’s Arkansas headquarters.

The illegal workers were all employed by a Wal-Mart contractor, officials said. But federal law enforcement personnel, who spoke on condition of anonymity, said recordings of meetings with contractors showed that some Wal-Mart executives knew about the immigration violations.

Federal agents executed a search warrant Thursday at Wal-Mart’s Bentonville, Ark., headquarters. A Wal-Mart spokeswoman said agents searched the office of a manager there and carried away several boxes.

“At this point we have no reason to believe that anyone will be indicted,” spokeswoman Sharon Weber said.

Wal-Mart is the world’s largest retail chain, with 4,259 stores around the globe and annual revenues last year of $247 billion. It is also the largest employer in the United States.

Weber said late Thursday that the company still was trying to understand the scope and details of the investigation. Wal-Mart has launched its own internal probe to determine what happened.

The company uses 100 contractors to do cleaning work at 700 of its stores, she said.

“We would never condone the use of illegal workers,” Weber said. “Integrity and honesty mean a tremendous amount to our company.”

Thursday’s bust arises from a 1998 investigation begun by the Pennsylvania Attorney General’s Office.

The raids were conducted at 60 stores Thursday by the Department of Homeland Security’s Bureau of Immigration and Customs Enforcement. Spokesman Garrison Courtney said those workers with no criminal history would be released with notices to appear before immigration judges at a later date. They could face deportation, Courtney said.

The raids took place in Alabama, Arkansas, Arizona, Connecticut, Delaware, Kentucky, Massachusetts, Maryland, Michigan, North Carolina, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and West Virginia.