The United States announced sanctions Tuesday on a China-based network for producing and distributing chemicals used to make drugs including those fueling a deadly national fentanyl crisis.

President Joe Biden's administration has made the fight against fentanyl a priority, with the synthetic opioid blamed for tens of thousands of deaths in recent years.

The sanctions targets include 25 individuals and entities based in China, alongside three other parties in Canada, the Treasury Department said in a statement.

In a separate notice, the Justice Department announced eight indictments charging China-based chemical manufacturing firms and staff with crimes related to drug production and distribution.

"We know that this global fentanyl supply chain, which ends with the deaths of Americans, often starts with chemical companies in China," Attorney General Merrick Garland told a press briefing.

He said it was "critical" that Beijing stops the "unchecked flow" of precursor chemicals coming from the country, adding that US officials will also raise the manufacturing and trafficking of fentanyl with their Mexican counterparts.

Tuesday's actions are aimed at exposing and disrupting a network "responsible for manufacturing and distributing illicit drugs," said Deputy Treasury Secretary Wally Adeyemo.

The China-based network is "responsible for the manufacturing and distribution of ton quantities of fentanyl, methamphetamine, and MDMA precursors," according to the Treasury.

The parties designated are also allegedly involved in trafficking xylazine -- a veterinary sedative known as "tranq" -- and nitazenes, which are often mixed with fentanyl or other drugs, posing a higher risk of a fatal overdose.

- Via Mexico cartels -

US authorities have noted that fentanyl is often coming from Mexican drug cartels that use precursor chemicals from China.

The Biden administration has imposed sanctions on cartels, although some politicians call for tougher actions.

Among the individuals designated on Tuesday are Wang Shucheng and Du Changgen -- members of a Chinese "syndicate" -- as well as their affiliates.

Wang was said to have directed others to establish companies used as cover to move pharmaceutical goods globally, while Du maintains the most influence over the organization, Treasury said.

The network is the "source of supply" for many US-based narcotics traffickers, dark web vendors, virtual currency money launderers and Mexico-based criminal organizations, Treasury added.

"Du Changgen and persons operating under him have been responsible for approximately 900 kilograms of seized fentanyl and methamphetamine precursors shipped to the United States and Mexico," the department said.

Companies Du owns have also been designated.

Hanhong Pharmaceutical Technology Co, found to be linked to several members of the network, was targeted -- alongside three representatives who were involved in its sale of fentanyl precursors and protonitazene.

Among others impacted were punch and die manufacturer Jinhu Minsheng Pharmaceutical Machinery and its part-owner, as well as other illicit drug distributors.

The United States has also blocked over a dozen virtual currency wallets.

The sanctions effectively stop those named from using the US financial system, and US citizens are barred from transacting with them.

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