The Associated Press

LITTLE ROCK, Ark. - Federal prosecutors have warned Wal-Mart Stores Inc. that the world's largest retailer is the target of a grand jury probe into the hiring of illegal immigrants, the company disclosed Tuesday.

Wal-Mart said it was not surprised to receive a so-called target letter after an investigation of floor-cleaning companies contracted by Wal-Mart led to mass arrests late last month.

Oct. 23, federal agents swept through 60 stores in 21 states, arresting about 250 allegedly illegal workers. Most worked for contractors, although 10 were Wal-Mart employees.

Sources said there was evidence that Wal-Mart executives knew of the immigration violations.

The grand jury will hear details starting in mid-December, said Wal-Mart spokeswoman Mona Williams.