Canadian border agents have seized a massive amount of carfentanil — a synthetic drug typically used to sedate elephants and other large wild animals, not to be confused with the synthetic opioid fentanyl.

This latest seizure comes as police forces and health officials continue to battle the scourge of opioid-related overdoses and deaths across North America.

At a press conference on Tuesday, officers with the Canada Border Services Agency (CBSA) announced they had intercepted a package at a Vancouver mailing center containing 1kg of the substance, enough to produce roughly 50 million doses. The package was bound for Calgary and was falsely marked as printer accessories. It originated from somewhere in China, as is the case with many illicit opioids stopped at the Canadian border.

After the Royal Canadian Mounted Police (RCMP) were notified and a lab confirmed the substance, a Calgary man was charged with two drug crimes related to carfentanil.

According to the RCMP, 20 micrograms of carfentanil (an amount smaller than a grain of salt) can kill the user.

It's the second time the CBSA in Vancouver have seized carfentanil, officers said. Border agents said the force has seized 84 shipments of fentanyl, the opioid 40 to 50 times stronger than heroin, from January 2010 to March of this year. According to other statistics obtained by VICE News, CBSA has seized three illicit fentanyl shipments coming into Canada from China from May to June of this year, including a kilogram bound for Toronto.

"It is hard to imagine what the impact could have been if even the smallest amounts of this drug were to have made its way to the street," George Stephenson, deputy of criminal operations for the RCMP K Division, said in a press release. "The illicit drug trade remains a dynamic and lucrative criminal activity that spans borders throughout the world."

Last month, an Ohio man was charged with selling carfentanil as heroin, in connection with one death and nine overdoses. The Associated Press reported that Chinese companies are selling it online, but it isn't yet pervasive in the illicit drug supply in the US. However, it has been suspected in a number of other recent overdoses in Kentucky and Florida.

The executive director of the American Association of Zoo Veterinarians told the AP that carfentanil is so powerful that zoo staff have to wear protective gear that covers their faces and bodies "because even one drop splattered into a person's eye or nose could be fatal."

Earlier this month, health officials sounded the alarm after dozens of overdose deaths associated with carfentanil and other illicit substances.