Canadian border officials have intercepted a one kilogram package of carfentanil bound for Calgary from China, a drug police say is so potent that amount could have produced millions of fatal doses.

Discovered by the Canada Border Services Agency (CBSA) in Vancouver in late June, the package was bound for an address in Calgary.

An investigation was launched between the CBSA, RCMP and Vancouver and Calgary police services.

Joshua Wrenn, 24, was arrested at his home July 5. He is charged with importation of a controlled substance and is scheduled to appear in court Oct. 19.

Wrenn's name and address were on the package, which was listed as being printer accessories, said Ana Maria Coutu, CBSA chief of operations at the Calgary International Airport.

"Upon inspecting the parcel … officers noted an unknown white substance," she said.


Carfentanil looks much like table salt, but the opioid is considered much more powerful than fentanyl. (CBC)

100 times stronger than fentanyl

One of the strongest opioids known, carfentanil is an analog of the synthetic opioid fentanyl, with police saying it has a quantitative potency 100 times higher.

Carfentanil looks much like table salt and police said a dose as small as 20 micrograms would be fatal to humans. There is also no known safe use of the drug in people.

"If you look at what one kilogram of carfentanil can produce, it's approximately 50 million fatal doses that could have hit our Canadian streets," said RCMP Insp. Allan Lai.

Alberta Health Service's Chief Medical Officer Karen Grimsrud said the drug is a concern. 

"​Well I think the concern is that people will get a drug that they don't really know what's in it, right? And so you purchase the drug and you think it's one thing and it turns out to be another, and so the concern is that you take this drug and you have an overdose as a result of it."

Fentanyl has been blamed for dozens of deaths across the province in recent months, including 69 between January and March of this year, according to AHS.