About half of the high-powered .50-caliber cartridges that the Mexican authorities have seized from cartels since 2012 were traced to an ammunition factory outside Kansas City, Mo., that is owned by the United States government, Mexico’s defense secretary said on Tuesday.
The factory, the Lake City Army Ammunition Plant, is the largest manufacturer of rifle rounds used by the American military.
Mexico’s defense secretary, Gen. Ricardo Trevilla Trejo, said about 137,000 .50-caliber rounds had been seized since 2012. Of those, he added, 47 percent came from Lake City and were sold in gun shops in the southern United States.
The revelation came in response to a reporter’s question about a recent joint investigation by The New York Times and the International Consortium of Investigative Journalists that exposed how Lake City ammunition — which has also been used by mass shooters in the United States — has become a staple for organized crime groups in Mexico.
General Trevilla Trejo also said that since October 2024, when Claudia Sheinbaum took office as president, the Mexican authorities had seized 18,000 firearms, of which nearly 80 percent came from the United States. Among the most destructive weapons seized, he added, were .50-caliber Barrett rifles, grenade launchers, rocket launchers and machine guns of various calibers.
On Monday, Ms. Sheinbaum said her administration was reviewing the reporting by The Times and the I.C.I.J. “so that we can talk to the U.S. government about this issue and understand how it’s possible that these weapons, which are for the exclusive use of the U.S. Army, are entering Mexico.”
The investigation found, in fact, that the .50-caliber cartridges made at Lake City were not restricted to the American military. The U.S. Army has allowed private contractors operating the Lake City plant to sell ammunition to distributors, resellers and retail stores — effectively making them available to the civilian market.
At least 16 online retailers have sold armor-piercing ammunition made at Lake City or made with components from the plant, according to a count by the I.C.I.J. and The Times.
“The irony is that the Mexican and U.S. governments want the same thing: to reduce deaths” caused by cartels, said Cecilia Farfán Méndez, the director of the North American Observatory at the Global Initiative Against Transnational Organized Crime. “But as long as criminal groups have easy access to these types of calibers and weapons, it’s as if they’re subsidizing the generation of this violence.”
The U.S. Army did not respond in detail to questions about the use of Lake City ammunition by drug cartels. A spokesperson previously said that allowing commercial sales from the plant saved taxpayers tens of millions annually.
Lake City rounds have ended up in the hands of Mexican cartel members, who have used them to terrorize civilians and security forces alike, according to documents obtained by reporters.
Armed with .50-caliber firearms, cartel gunmen have downed helicopters, assassinated government officials, shot at police and military forces, and killed civilians.
“The armor we have cannot protect our personnel from the type of penetration this cartridge is capable of,” Luis Cresencio Sandoval, General Trevilla Trejo’s predecessor as Mexico’s defense secretary, told reporters in 2024. He was referring to a .50-caliber round from Lake City that had been used to attack a military convoy in northern Mexico, killing one soldier and injuring three others.
Mexico has tight restrictions on who can buy and own guns, which can be legally purchased only at two Mexican Army-run stores. Still, most types and calibers are exclusively reserved for the military and law enforcement. The Mexican government has estimated that 200,000 to 500,000 firearms are illegally trafficked into Mexico from the United States each year.
Last year, the U.S. Supreme Court unanimously dismissed a lawsuit filed by the Mexican government against major U.S. manufacturers, which argued that the companies had aided and abetted unlawful gun sales that routed firearms to Mexican drug cartels. In its ruling, the court said that the manufacturers’ “failure to stop” independent retailers from making unlawful sales did not meet the high legal bar for aiding and abetting.
But the court acknowledged Mexico’s claim that U.S. guns were being sold to Mexican traffickers. “We have little doubt that, as the complaint asserts, some such sales take place — and that the manufacturers know they do,” the ruling said.
Mexico filed a separate lawsuit in Arizona against five gun dealers. That case is pending.
Ms. Sheinbaum has consistently called for greater cooperation from the Trump administration to stop the flow of U.S.-made weapons and ammunition into Mexico, often comparing it to the pressure from Washington to get her country to end fentanyl trafficking.
Some joint initiatives have emerged to increase inspections and seizures on both sides of the border, and to share more information between governments. But in an exclusive interview last year, Omar García Harfuch, Mexico’s security secretary, told Times reporters that U.S. efforts to cut the supply of weapons had “not been enough.”
If Mexican cartels found it more difficult “to obtain those types of weapons,” Mr. Harfuch added, “it would definitely be a different fight.”
Ben Dooley and David Shortell contributed reporting.
Emiliano Rodríguez Mega is a reporter and researcher for The Times based in Mexico City, covering Mexico, Central America and the Caribbean.
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