MEXICO CITY - The former mayor of the southwestern city of Iguala has been charged with last year’s kidnapping of 43 students who are feared to have been killed, a top security official said. Tomas Zeron, director of criminal investigations at the federal Attorney General’s office, said that prosecutors had obtained an arrest warrant for former mayor Jose Luis Abarca and 44 others on charges of kidnapping the 43 students. President Enrique Pena Nieto is facing his deepest crisis over the government’s handling of the investigation. Anger over the case spurred sometimes violent demonstrations around the country late last year.