Riots broke out simultaneously at seven Guatemalan prisons this week, leaving 31 inmates dead in an apparent gang feud. The fighting began with two grenade blasts at a former police barracks in downtown Escuintla, where 400 gang members were being held. The violence quickly spread to other prisons, demonstrating the ability of leaders of the powerful Mara Salvatrucha and MS-18 gangs to direct their members from behind bars using cell phones, messengers, and other methods. The gangs maintain constant communication, said Interior Minister Carlos Vielmann. They have a Web page and not only synchronize in Guatemala, they synchronize with El Salvador, Honduras, and with the United States.