FBI agents arrested over 250 Wal-Mart employees from 62 stores in 21 states Thursday. The workers, members of cleaning crews hired through a contractor, were arrested as they finished their night shifts. A spokesperson from Immigration and Customs Enforcement said that all of the workers were in the U.S. illegally. The employees now face deportation.

The investigation prompted allegations that Wal-Mart subcontractors recruited illegal immigrants, mostly Eastern Europeans, to work on cleaning crews at various Wal-Mart stores. Most of the arrests took place in Pennsylvania and Texas stores.

In what is the largest immigration crackdown in several years, federal agents also searched the office of an executive at Wal-Mart's Bentonville, AR., headquarters, removing boxes of documents.

A Wal-Mart company spokesperson said the allegations that illegal immigrants were working in company stores came as a surprise.

Officials said the arrests were prompted by two earlier federal investigations, one in 1998 and one in 2001. The 1998 investigation, conducted with the Pennsylvania attorney general’s office, also targeted the contractors and subcontractors used by Wal-Mart for cleaning services.

Wal-Mart Vice President for Communications Mona Williams said, "These federal officials are referring to third-party suppliers that we entrusted to hire legal workers. For them to say that it strains credibility that we're surprised about what happened today, those other actions happened years ago."

An anonymous official quoted by the New York Times said the government used wiretaps in the investigation and had recordings of conversations among Wal-Mart executives and contractors.

Employers are required to check I-9 forms completed by every new employee and retain the forms for a certain period of time. Employers who knowingly hire illegal immigrants can face both civil and criminal penalties, including a $10,000 fine per illegal employee.

However, because the workers were employed on a contract basis by another employer, the government will have the more difficult task of showing that Wal-Mart was aware that the contractors were hiring undocumented workers and knowingly contracted with them anyway.

This is the second major operation against a large American company undertaken by the Bush Administration since the 9/11 attacks. The other action was against Tyson Foods. Wal-Mart and Tyson are two of the largest employers in Arkansas, home of former President Bill Clinton.

Critics of the raids have questioned whether it is wise for the government to focus so much time and effort targeting illegal janitors when the country is at war fighting terrorists interested in destroying the country. They also suggest that the raid actually reinforces the need for comprehensive immigration reform so that there are legal and practical ways for companies to actually bring in much needed low-skilled immigrant labor.