The US on Thursday imposed sanctions on senior members of the armed wing of a Mexican drug cartel that operates in and around the border territories of Chihuahua, Mexico. The cartel was also linked to the 2019 ambush that killed nine Americans in Mexico.

Five Mexican nationals and two companies linked to La Linea, a violent drug-smuggling organization in Mexico fentanyl and other synthetic drugs into the US on behalf of the transnational Juarez cartel, were hit by economic sanctions Thursday.

The latest action is aimed at preventing a major source of fentanyl from entering the US; the powerful opioid is the deadliest drug in the US today. The Centers for Disease Control and Prevention states that drug overdose deaths in the US increased more than sevenfold between 2015 and 2021, although the agency reported a 3% drop in drug overdose deaths this year.

Mexico and China are the primary sources of fentanyl and fentanyl-related substances trafficked directly into the US, according to the Drug Enforcement Administration, which is tasked with combating illicit drug trafficking. Almost all of them precursor chemicals which are necessary for the fentanyl to come from China.

La Linea and the Juarez cartel are known for violence against innocent people, and US authorities have tried to go after them – in July 2022, a federal judge in North Dakota forced La Linea to pay $4.6 billion in monetary damages for the families of nine Americans killed in an ambush in northern Mexico on November 4, 2019.

Treasury Undersecretary Wally Adeyemo said in a statement Thursday that “if La Linea continues to directly contribute to the proliferation of deadly fentanyl in our communities, Treasury will continue to use every tool in our arsenal to pursue their criminal activity “.

The Biden administration has taken a series of actions against fentanyl traffickers — charging powerful traffickers with drug and money laundering crimes and announcing indictments and sanctions against Chinese companies and executives accused of importing chemicals used to make the dangerous drug.

In December 2023, Treasury Secretary Janet Yellen launched a Fentanyl Strike Force that brings together personnel and intelligence from across the Treasury Department—from sanctions and its intelligence arms to IRS Criminal Investigations—to work together more effectively to stop the flow of drugs in the country.

And President Biden signed into law the bipartisan FEND off Fentanyl Act as part of the supplemental spending package signed in April, which, among other things, declares international fentanyl trafficking a national emergency.

Combating fentanyl has increasingly become a political issue. Republicans say fentanyl smuggling across the US-Mexico border should be viewed alongside immigration issues, which are a focal point of the 2024 presidential election.

Republican presidential candidate Donald Trump has blamed migrants for trafficking drugs like fentanyl, even though federal data suggests many people smuggling fentanyl across the border are American citizens.

Over the past two years, the Treasury has sanctioned more than 350 individuals and firms linked to drug trafficking, from cartel leaders to laboratories and suppliers.

Last month, the US sanctioned a man known as “The Tank” who allegedly runs the fuel-theft arm of hyperviolent Mexico The Jalisco New Generation cartel .

In July, the US imposed sanctions on a group of Mexican accountants and firms believed to be linked to a limited duration fraud ring run by the Jalisco cartel in a multi-million dollar scheme targeting Americans.

A month earlier, US officials announced economic sanctions against eight targets affiliated with a Mexican drug cartel, La Nueva Familia Michoacana, accused of fentanyl trafficking and people smuggling. Among the leaders targeted was an alleged assassin named Uriel Tabares Martinez. According to the Treasury Department, he is known as “El Medico” (“The Doctor”) for the violent and surgical manner in which he cakes and kill those who cross the high-ranking members of the cartel.