Mexico - At Least 31 Inmates Are Killed in Prison Gang Riot - NYTimes.com A battle between rival gangs inside a prison in northern Mexico left at least 31 inmates dead in the latest violence to erupt inside the country's overcrowded penal institutions, local officials said on Wednesday. Clashes between prisoners wielding knives and homemade weapons began about midday and were controlled several hours later in Altamira, a city on the Gulf of Mexico in Tamaulipas State, said a state government spokesman, Guillermo Martínez. At least 13 other inmates were injured, the state government said. Powerful drug cartels are fighting for control of smuggling routes along Mexico's border with the United States, and rivalries often spread into the prison system, where inmates held on federal drug charges are mixed with other criminals.