MEXICO CITY - The U.S. Border Patrol arrested a Mexican immigration official who was allegedly trying to help a group of undocumented migrants sneak into the United States, the Mexican government said Sunday.

Immigration agent Francisco Javier Gutierrez was arrested at a checkpoint near Alamogordo, N.M., about 100 miles north of the U.S.-Mexico border, the Mexican Interior Department said in a news release.

Gutierrez had been fired on corruption allegations last year but returned to his job after winning a court case in which he claimed he had been unfairly dismissed, according to the National Immigration Institute...