SAN FERNANDO, Mexico – Two cars exploded early Friday in a northern state where officials are investigating the killing of 72 Central and South American migrants, while a prosecutor investigating the massacre has disappeared. The prosecutor, Roberto Jaime Suarez, disappeared Wednesday in the town of San Fernando, where the bodies of the migrants were found, the Tamaulipas state attorney general's office said in a statement. A transit police officer in the town is also missing. President Felipe Calderon, speaking during a forum on security, said Suarez, a Tamaulipas state prosecutor, was involved in the initial investigation of the massacre, which...