A prison riot Wednesday in the troubled Mexican border town of Juarez left 20 dead and 15 wounded, an official said. None of the dead were police or military officials, said Enrique Torres, a spokesman for the joint operation at the Cereso Estatal de Ciudad Juarez prison. Authorities called in 200 federal police agents and 50 army soldiers to help put down the riot; two helicopters and an airplane also were employed, he said.