Mexico City, Mexico - As investigators continued their search for the gunmen who kidnapped four Americans in the border city of Matamoros last week, Mexican President Andrés Manuel López Obrador lashed out at Republican US lawmakers who have proposed sending troops into Mexico, telling them that the United States should concentrate on curbing its rampant appetite for illegal drugs.

"Why don't you take care of your young people? Why don't you take care of the serious problem of social decomposition? Why don't (you) temper the constant increase in consumption of drugs?" López Obrador asked Thursday at his daily news conference.

López Obrador's unusually sharp comments came two days after Mexican authorities located the missing Americans in a shack on the outskirts of Matamoros, a notoriously dangerous city long disputed by rival drug trafficking groups.

Two of the Americans, Shaeed Woodard (33) and Zindell Brown (28), were found dead, according to Mexican authorities.

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Two others, Latavia McGee (33) and Eric James Williams (38), were found alive and quickly transported across the border.

US and Mexican authorities say they still don't know why the tourists, who entered Mexico on Friday so that McGee could undergo a medical procedure, were fired upon by several men and later thrown in the back of a pickup truck and hauled away.

On Thursday, law enforcement sources in Tamaulipas state circulated a letter that appeared to be from a local drug cartel that blamed the kidnapping on several rogue members of the group.

Citing unnamed sources, the Associated Press said the cartel had turned over five of its members to authorities. That has not been confirmed by Mexican authorities or the FBI, which is helping in the investigation.

Whatever the cause of the kidnapping, it has clearly provoked big reactions on both sides of the border, inflaming a long-standing debate about who is responsible for rampant violence in Mexico and the best way to curb it.

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Multiple Republican lawmakers pointed this week to the kidnapping as further evidence of Mexico's supposed lawlessness – and the US need to intervene.

Citing an explosion in recent years of American deaths from fentanyl, Republican members of Congress had already been pushing a bill that would allow US armed forces to fight crime in Mexico, and several states had asked that federal authorities label drug cartels as terrorist groups.

In Mexico, that kind of rhetoric has been met wearily.

Mexicans have long complained that their nation has the geographic misfortune of sitting next to the United States, the world's biggest consumer of illicit drugs and the site of the world's largest stockpile of firearms. Despite Mexico's extremely strict gun laws – there is just one gun store in the entire country – it is flooded daily with weapons smuggled illegally from the US.

A US-backed effort to confront drug cartels with the Mexican military backfired, leading to an explosion of violence across Mexico over the last 15 years. It also failed to reduce the quantity of drugs arriving in the United States.

López Obrador has frequently criticized a militarized approach to combating drug trafficking, accusing his predecessors of turning Mexico into "a graveyard," even though his own crime-fighting strategy hasn't varied much from theirs in practice.

At his news conference Thursday, López Obrador dismissed Republican threats of US military intervention as election "propaganda."

To fight the scourge of fentanyl, he said, the US should look within its own borders.

"We are very sorry for what is happening in the United States, but why don't they attend to the problem?" he said. "Why don't they fight the distribution of fentanyl in the United States, the cartels in the United States that are in charge of distributing fentanyl?"

"Here we do not produce fentanyl and we do not consume fentanyl," he insisted, despite ample evidence to the contrary.

The production of fentanyl in Mexico is well documented. Last month, Mexican soldiers raided a drug lab in Sinaloa state and seized 630,000 pills containing fentanyl and 282 pounds of fentanyl powder, and use of the drug south of the border has been rising, along with general consumption of illicit drugs, although at nowhere near the levels of US consumption.

López Obrador, who is popular in Mexico and among Mexicans living in the United States, threatened to weaponize US Latino voters against the Republican Party if they don't stop their calls for military intervention in Mexico.

He said his government was launching an "information campaign" to show Mexican Americans and other Latinos "how this initiative by the Republicans, in addition to being irresponsible, is an offense to the people of Mexico and shows a lack of respect for our independence and our sovereignty."

"If they don't change their attitude and think that they are going to use Mexico for their propaganda, electoral and political purposes, we are going to call for people not to vote for that party," he said.

But in Mexico, where López Obrador's party will also face a consequential election in 2024, many were questioning who gets justice and why.

In this country, where the vast majority of crimes are never solved and there are 110,000 Mexicans who are missing, or "disappeared," the quick rescue of the Americans stung.

Noting "the speed and coordination" of the kidnapping response, Television journalist Ana Francisca Vega seemed to speak for many when she lamented this week the "thousands of disappeared Mexicans who have no such luck."