Stockpiles captured by Mexican soldiers show that warring traffickers are now obtaining military-grade weaponry such as grenades, launchers, machine guns, mortars and anti-tank rockets.
Some drug gangs have even sought explosive material that some experts worry could be used in car bombs and improvised explosive devices of the kind used in Iraq and Afghanistan. Soldiers found 14 sticks of TNT among an arsenal of hundreds of rifles and grenades seized in November from a house in Reynosa, across the border from McAllen, Texas.
But so far, attempts at using bombs have been unsuccessful as drug gangs haven't yet developed the skills to build effective ones, said Stephen Meiners, a Latin America analyst with Stratfor, a private U.S.-based group. Authorities suspect the Sinaloa cartel tried to kill a Mexico City police officer last year with a homemade bomb that killed only the attacker.
"Once you have a bomb maker that has mastered that skill, unless that bomb maker is caught, he can keep constructing those devices and send them out to be deployed," he said.
One of the most worrisome weapons yet was seized this week just south of Nogales, Ariz.: a powerful gun mounted on the back of an SUV and protected by a thick metal shield. Police said it belonged to one of the Beltran Leyva drug gangs.
Mexican and U.S. authorities disagree on just what type of gun it was. Federal police coordinator Gen. Rodolfo Cruz maintains it was .50-caliber anti-air craft machine gun. ATF, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, said it was an unmodified .50-caliber semiautomatic rifle made by TNW, a U.S. firearms manufacturer.
ATF investigators traced the gun - along with seven others seized at a house in Sonora state on Monday - to suppliers in the United States, said Bill Newell, special agent in charge of the ATF in Arizona and New Mexico.
Even as the governments try to choke off the U.S. weapons supply, the gangs are clearly trying to expand their arsenals beyond the assault rifles and semi-automatics they can get in the United States.
These and other, much heavier weapons are readily available on the global black market, particularly from stockpiles left over from Central America's civil wars.
Civilians are increasingly being targeted. In October, assailants hurled a grenade at the U.S. consulate in the northern city of Monterrey. In January, a TV network's offices in the same city were attacked.
The grenades used in both attacks were similar to one thrown into a nightclub in Pharr, Texas, in January, according to the ATF. That one didn't explode.
The agency suspects they came from a Monterrey warehouse where the Gulf cartel had been stockpiling weapons, including South Korean-made K75 fragmentation grenades.