MEXICO CITY—Mexico's government is reversing course from its initial hands-off attitude toward allegations of corruption and influence-buying by Wal-Mart in Mexico. The federal Attorney General's Office now says it's opening a preliminary investigation into the charges against the country's largest private employer.

President Felipe Calderon has cited Wal-Mart's growth in Mexico as one of his administration's successes, but on Wednesday he said he was "very angry" about the allegations first reported by The New York Times.

The Attorney General's Office said Thursday it will look into potential wrongdoing by individuals, business and government officials. The government's anti-corruption office has said it will look into federal permits granted to Wal-Mart.

The Mexican government originally said it had no basis for involvement because the allegations involved officials at the state and local level.