The kidnapping in Mexico this week of four U.S. citizens that left two of them dead has renewed the focus on the politically charged issue of southern border security and prompted calls from some lawmakers for the Biden administration to more seriously crack down on cartels.

Biden administration officials called the killings “unacceptable” — potentially escalating tensions around the already fraught issues of border security and U.S.-Mexico relations as authorities work to learn more about the circumstances of the incident.

U.S. and Mexican authorities had been searching for four Americans who were kidnapped last Friday after crossing the border for a trip to get a medical procedure. Two of the Americans were found dead on Tuesday. One of the others was found injured, and the fourth is alive.

The FBI had said unidentified gunmen started firing at the four Americans’ vehicle shortly after it crossed into Mexico. They were then taken from the scene by armed men. Officials have not said whether the four Americans were deliberately targeted in the attack.

“Attacks on U.S. citizens are unacceptable no matter where or under what circumstances they occur,” John Kirby, a national security spokesperson for the White House, told reporters Tuesday. “And we’re going to work closely with the Mexican government to make sure justice is done in this case.”

Kirby said it was too soon to discuss any potential policy changes that would stem from the attack, but some lawmakers were quick to offer up legislative prescriptions.

Sen. Lindsey Graham (R-S.C.) said Monday on Fox News that he was ready to introduce a measure that would classify certain Mexican drug cartels as terrorist organizations and “set the stage” for the U.S. to use military force in Mexico in the wake of the kidnapping.

“I would tell the Mexican government if you don’t clean up your act, we’re going to clean it up for you,” Graham said.

Other Republicans, such as Rep. Chip Roy (R-Texas), have previously argued for designating cartels as terrorist organizations, and the deadly kidnapping just over the border has renewed those calls.

Attorney General Merrick Garland on Tuesday told reporters that agencies like the Drug Enforcement Administration (DEA) and the FBI “are doing everything possible to dismantle and disrupt and ultimately prosecute the leaders of the cartels and the entire networks that they depend on.”

More broadly, the incident in the city of Matamoros has given Republicans another opening to lob political attacks at the White House over its immigration record.

GOP lawmakers have for months argued the Biden administration has not done enough to curb the flow of migrants and drugs at the southern border, suggesting that what they see as the president’s lax approach to border security is resulting in violence.

“Four Americans were kidnapped by a Mexican cartel. Two are dead. There’s no chance the cartel would be SO BOLD if America had a president who took border security seriously. We are a laughingstock because of Biden’s weak leadership,” Rep. Kevin Hern (R-Okla.), chairman of the influential Republican Study Committee, tweeted Tuesday.

The White House on Tuesday pushed back against criticisms that Biden’s border policies are connected to the latest instance of violence across the border.

Officials noted that Biden recently signed an order giving expanded authority to the Treasury Department to penalize cartels, that the Department of Homeland Security screens and vets each individual encountered at the border, and Biden has backed funding for increased border security measures.

Stopping the flow of fentanyl across the border has also been a top priority for Biden, officials said, and they noted that U.S. authorities last year seized twice as many drugs as the amount confiscated in 2020 as part of efforts to crack down on drug traffickers.

The State Department has issued a travel advisory for the area where the incident took place telling Americans to avoid it due to the risk of crime and kidnapping.

The U.S. and Mexico have for years been engaged in at times tense discussions over the issues of migration and cracking down on cartels. During the last administration, then-President Trump at one point claimed drug cartels were “in control” of the area south of the U.S. border, and at another point called on Mexico to “wage war” on cartels and “wipe them off the face of the earth,” a plea that was rebuffed by Mexican President Andrés Manuel López Obrador.

Biden traveled to Mexico in January to meet with López Obrador to talk about border security and migration issues. The U.S.-Mexico tensions were at times on full display during the visit, including when López Obrador implored Biden to do away with “disdain” for the region.

“This is the moment for us to determine to do away with this abandonment, this disdain, and this forgetfulness for Latin America and the Caribbean,” he said.

The issue of border security and how best to combat violent drug cartels is sure to linger beyond this week’s deadly kidnapping and well into the next election.

Former President Trump, who is running for the GOP’s 2024 presidential nomination and has made border security the center of his campaigns, earlier this year offered his vision for getting aggressive toward cartels. 

Trump, in a pre-recorded video released in January, said he would order the Pentagon to use special forces, cyber warfare and other actions “to inflict maximum damage on cartel leadership, infrastructure and operations,” and he pledged to ask Congress to legislation ensuring convicted drug smugglers and traffickers receive the death penalty.