(CBS News) - Canadadrugs.com bills itself as the "largest and most trusted" online Canadian pharmacy. Based in an office building in Winnipeg, Manitoba, it says it sells medications to people in 135 countries, including the United States.
"We're an international mail order pharmacy," says the company's chief business development officer, Brock Gunter-Smith. "We started 11 years ago. And we're just like any other pharmacy that you might deal with in your local neighborhood, except we send medications by mail."
It's not that simple when it comes to buying drugs online.
"No drugs that are being shipped via the Internet to U.S. consumers from these websites we've identified actually come from Canada or have actually been approved by Health Canada," said Carmen Catizone, executive director of the National Association of Boards of Pharmacy.
Watch the first part of Keteyian's investigation into fake Avastin
"We're quite proud of what we do in working with licensed pharmacy partners," said Gunter-Smith. "Each one of our pharmacy partners undergoes inspection and has licensure from local and national regulatory authorities."
CBS News has learned that one of Canadadrugs.com's key suppliers is Tom Haughton, who admits his company was responsible for shipping at least 36 vials of counterfeit Avastin into the U.S. last year.
Last month, the FDA sent letters to 19 U.S. doctors and clinics, warning they may have purchased counterfeit vials of the life-saving cancer drug.
A federal grand jury has been convened, and subpoenas have gone out to the 19 medical clinics. They're still backtracking this Avastin, trying to find the original source.
Haughton owns several pharmaceutical-related businesses in Barbados, and some 3,000 website domain names. Many take you to Canadadrugs.com.
"We've worked with Tom for quite some time. And, he's one of our trusted partners," Gunter-Smith said.
Watch the second part of Keteyian's investigation into fake Avastin
"We didn't buy it out of someone's trunk of the car," Haughton said. "We bought it through a licensed and registered wholesaler."
It's not his fault?
"It's my fault that my company sold this product," Haughton said. "But I'm telling you we sourced it from the controlled and regulated EU supply chain that millions of people trust every day."
Regardless of the source, according to the U.S. Food and Drug Administration, it is illegal for pharmacies based in Canada or other countries to ship prescription drugs into the U.S..
"Canada Drugs is not licensed in any of the U.S. states," Cadizone said. "What that means is that they are not allowed to legally ship products to the U.S. They are violating state law every time they ship a package into the U.S. to a U.S. patient."
In a statement, Canadadrugs.com said it "has been legally licensed to carry on business as an international prescription service pharmacy by the Manitoba Pharmaceutical Association. Its pharmacies follow all laws and regulatory requirements in the jurisdictions where they operate."
Canadadrugs.com says its company had nothing to do with the fake Avastin. But regulators and law enforcement officials tell CBS News this is exactly why it's illegal to sell unapproved drugs from overseas in the U.S.