WASHINGTON — The Biden administration took aim Tuesday at the fentanyl trafficking threat, announcing a series of indictments and sanctions against Chinese companies and executives blamed for importing the chemicals used to make the deadly drug.

Officials described the actions, which include charges against eight Chinese companies accused of advertising, manufacturing and distributing precursor chemicals for synthetic opioids like fentanyl, as the latest effort in their fight against the deadliest overdose crisis in U.S. history. The moves come one day before senior administration officials are set to visit Mexico, whose cartels are part of the global trafficking network, for meetings expected to involve discussion of the drug threat.

“We know that this network includes the cartels’ leaders, their drug traffickers, their money launderers, their clandestine lab operators, their security forces, their weapons suppliers, and their chemical suppliers,” Attorney General Merrick Garland said at a news conference. “And we know that this global fentanyl supply chain, which ends with the deaths of Americans, often starts with chemical companies in China.”

Besides charging eight companies, the Justice Department also indicted 12 executives for their alleged roles in drug trafficking. In a coordinated action, the Treasury Department announced sanctions against 28 people and companies — mostly in China but also in Canada — that will cut them off from the U.S. financial system and prohibit anyone in the U.S. from doing business with them. None of those charged has been arrested, but Garland said prosecutors intended to “bring every one of these defendants to justice.”

“It’s the latest step in the rapid scaling up of our work targeting the financial flows that power the global illicit drug trade,” said Deputy Treasury Secretary Wally Adeyemo. He said Treasury is also seeking out the friends, family members, and affiliates of the people who benefit from drug sales.

“If you benefit from the proceeds of this illicit activity, we are going to come after your assets,” he said.

Mexico and China are the primary sources for 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. And the companies that make the precursors routinely use fake return addresses and mislabel the products in order to avoid being caught by law enforcement.

One of the examples cited by the Justice Department involves a Chinese pharmaceutical technology company that advertised xylazine, a horse tranquilizer that is often mixed to fentanyl to ensure a more potent high, and shipped the chemicals to the U.S. and to Mexico. One of the purchasers in Mexico, officials said, was a drug trafficker associated with the Sinaloa Cartel.

This latest action follows a series of measures taken this year against members of the Sinaloa cartel, cash couriers and cartel fraud schemes.

Republicans have complained, however, that the administration isn’t doing enough to stop fentanyl and the issue is likely to figure prominently in next year’s presidential campaign.

In February, 21 Republican state attorneys general wrote a letter to President Joe Biden and Secretary of State Antony Blinken calling on them to designate Mexican drug cartels as foreign terrorist organizations. Last year a group of Republican attorneys general asked the president to declare fentanyl a weapon of mass destruction. No such actions have been taken.

Fentanyl, a powerful opioid, is the deadliest drug in the U.S. today. The Centers for Disease Control and Prevention states that drug overdose deaths have increased more than sevenfold from 2015 to 2021.

More than 100,000 deaths a year have been linked to drug overdoses since 2020 and about two-thirds of those are related to fentanyl. The death toll is more than 10 times as many drug deaths as in 1988, at the height of the crack epidemic.

The U.S. has taken a slew of actions to stem the tide of fentanyl coming into the country. Overall, the Biden administration has imposed over 200 sanctions related to the illegal drug trade.

State lawmakers nationwide are responding to the deadliest overdose crisis in U.S. history by pushing harsher penalties for possessing fentanyl.

In a speech at the Family Summit on Fentanyl last week, Garland said the Justice Department was sending out some $345 million in federal funding over the next year, including money to support mentoring for at-risk young people and increase access to the overdose-reversal drug naloxone.

On Capitol Hill, a bipartisan group of legislators out of the Senate Banking and Armed Services committees has introduced legislation that would declare fentanyl trafficking a national emergency and prod Treasury to use its sanctions authority to quell the proliferation of the drug in the U.S.

It would also impose reporting requirements and enable the president to confiscate sanctioned property of fentanyl traffickers to use for law enforcement efforts.