Meanwhile, the authorities in the Pacific coast state of Nayarit say the death toll after a gun battle between rival gangs has now risen to at least 29.

BBC: Mexico gang violence displaces thousands in Michoacan

That nickname has accrued to I-95, a highway running along America's east coast from Miami all the way to Maine, which gun traffickers have long used to haul guns bought in southern states with relatively lax purchasing laws to sell in north-eastern states such as New York and New Jersey, which more strongly regulate gun sales.

ECONOMIST: Guns and state borders