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

Five Mexican citizens and two companies linked to La Linea, a violent Mexico-based drug trafficking organization that smuggles fentanyl and other synthetic drugs into the U.S. on behalf of the transnational Juarez Cartel, were hit with economic sanctions Thursday.

The latest action is meant to stem a major source of the fentanyl coming into the U.S; the powerful opioid is the deadliest drug in the U.S. today. The Centers for Disease Control and Prevention states that drug overdose deaths in the U.S. have increased more than sevenfold from 2015 to 2021, though the agency reported a 3% decline in the number of drug overdose deaths this year.

Mexico and China are the primary sources of fentanyl and fentanyl-related substances trafficked directly into the U.S., according to the Drug Enforcement Administration, which is tasked with combating illicit drug trafficking. Nearly all the precursor chemicals that are needed to make fentanyl come from China.

La Linea and the Juarez Cartel are known for inflicting violence on innocent people, and U.S. authorities have tried to pursue them – in July 2022, a North Dakota federal judge ordered La Linea to pay $4.6 billion in monetary damages to the families of nine Americans killed in an ambush in Northern Mexico on Nov. 4, 2019.

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

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

In December 2023, Treasury Secretary Janet Yellen launched a Counter-Fentanyl Strike Force that brings together personnel and intelligence from throughout the Treasury Department — from its sanctions and intelligence arms to IRS Criminal Investigations – to more effectively collaborate on stopping the flow of drugs into 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 that the international trafficking of fentanyl is a national emergency.

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

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

Over the past two years, Treasury has sanctioned more than 350 people and firms connected to drug trafficking, from cartel leaders to labs and suppliers.

Last month, the U.S. sanctioned a man known as “The Tank” who allegedly leads the fuel theft arm of Mexico’s hyper-violent Jalisco New Generation cartel .

In July, the U.S. imposed sanctions on a group of Mexican accountants and firms allegedly linked to a timeshare fraud ring run by the Jalisco cartel in a multi-million dollar scheme targeting Americans.

The month before that, U.S. officials announced economic sanctions against eight targets affiliated with a Mexican drug cartel, La Nueva Familia Michoacana, accused of fentanyl trafficking and human 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 tortures and kills those who cross the high-ranking members of the cartel.