US officials have arrested 250 workers at retail giant Wal-Mart, as part of a clampdown on the hiring of illegal immigrants.
Wal-Mart insiders turned a blind eye, officials say
The US Immigration and Customs Enforcement (ICE) Bureau, part of the new Department of Homeland Security, said the immigants were hired by a contract cleaning firm, and that Wal-Mart executives had turned a blind eye to the practice.
The ICE's investigation, known as "Operation Rollback", targeted workers at 61 Wal-Mart stores in 21 states.
Investigators are still pursuing at least 50 workers.
According to ICE, some Wal-Mart officials had direct knowledge of the recruitment of illegal immigrants.
Federal agents have reportedly conducted searches at Wal-Mart's Arkansas headquarters.
And federal grand jury subpoenas have
been issued for the Wal-Mart executives to testify.
Wal-Mart said it was "committed to
cooperating" with federal officials, and stressed that it was not directly responsible for the behaviour of third-party contractors.
The probe is another stroke of bad news for Wal-Mart, the world's biggest retailer.
The firm already faces a wave of lawsuits alleging sexual discrimination, and has been criticised for its apparently anti-union stance.