NEW : The attackers are believed to be Central and South American migrants crossing Mexico . Brazil says at least two Brazilians were among the dead . A naval officer was killed and three of the delinquents were killed , '' said an officer who answered the telephone at the navy 's communication department . Mexico says they are extorting migrants as Mexican government weakens cartels . Two policemen and a member of the Mexican military were killed in a shootout .
NEW : The attackers are believed to be Central and South American migrants crossing Mexico . Brazil says at least two Brazilians were among the dead . Mexico says they are extorting migrants as Mexican government weakens cartels . Two policemen and a member of the Mexican military were killed in a shootout .