The dozen packages were shipped from China to mail centers and residences in Southern California.

One box was labeled as a “Hole Puncher.”

In fact, it was a quarter-ton pill press, which federal investigators allege was destined for a suburban Los Angeles drug lab.

The other packages, shipped throughout January and February, contained materials for manufacturing fentanyl, an opioid so potent that in some forms it can be deadly if touched.

When it comes to the illegal sale of fentanyl, most of the attention has focused on Mexican cartels that are adding the drug to heroin smuggled into the United States.

But Chinese suppliers are providing both raw fentanyl and the machinery necessary for the assembly-line production of the drug powering a terrifying and rapid rise of fatal overdoses across the United States and Canada, according to drug investigators and court documents.

“We have seen an influx of fentanyl directly from China,” said Carole Rendon, the acting US attorney for the northern district of Ohio in Cleveland. “It’s being shipped by carrier. It’s hugely concerning because fentanyl is so incredibly deadly.”

The China connection is allowing local drug dealers in North America to mass produce fentanyl in pill form, in some cases producing tablets that look identical to an oft-abused version of the prescription painkiller OxyContin. It also has been added to Xanax pills. And last week, fentanyl pills made to resemble the painkiller hydrocodone were blamed for a wave of overdoses in the Sacramento area, including nine deaths.

The fentanyl pills are often disguised as other painkillers because those drugs fetch a higher price on the street, even though they are less potent, according to police.

The Southern California lab was just one of four dismantled by law enforcement in the United States and Canada in March.

In British Columbia, police took down a lab at a custom car business that was allegedly shipping 100,000 fentanyl pills a month to nearby Calgary, Alberta where 90 people overdosed on the drug last year. The investigation began when border authorities intercepted a package in December containing pharmaceutical equipment. Police would not describe the equipment but told STAT it came from China.

Federal agents shut down a Seattle lab set up in the bedroom of a home in a residential neighborhood. Similarly, investigators last week raided a suburban Syracuse, N.Y. residence that police charged was a “Fentanyl Processing Mill.” Investigators found six people inside the home mixing and packaging the drug and seized enough fentanyl to make 5,866 doses. As they entered the home, police reportedly were warned by the alleged dealers not to touch the fentanyl without gloves because of its potency.

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