U.S. investigators are looking at pharmacy companies with possible Canadian connections as they seek the source of fake cancer drugs.

A vial and package for the cancer drug Avastin are shown in this supplied product image. A fake version of the drug was recently distributed to doctors in three U.S. states, authorities have found. (Genentech/Associated Press)

The U.S. Food and Drug Administration issued a warning last month that a counterfeit version of Avastin, a popular cancer drug, had been purchased and used by 10 medical practices in three American states.

In the counterfeit versions of the drug, believed to have come from Egypt and Turkey via several European countries, the active ingredient was replaced with starch, cleaning solvents and other chemicals, authorities found.

The FDA is investigating three specific distributors that are believed to have connections to companies owned by Thomas Haughton, a Canadian based in Barbados.

"You have to look at where they get these drugs," Shelly Burgess, a spokesperson for the FDA, told CBC News on Wednesday.

"Nearly all of these drugs that come into the U.S. via international mail or courier violate the Food, Drug and Cosmetic Act in some way."

Avastin is used to treat cancers of the colon, lung, kidney and brain. The drug is one of the most widely used cancer drugs in the world, generating about $6 billion US a year in sales.

No fake Avastin in Canada

Officials with Roche, the Swiss company that makes Avastin, said they believe none of the counterfeit drugs have made it to Canada.

The Wall Street Journal reported Wednesday that Haughton, who operates a network of drug distributors selling to U.S. doctors, has acknowledged his companies shipped a counterfeit version of Avastin late last year.

Haughton told the newspaper he was horrified to discover his companies had shipped the fake cancer drugs.

The Wall Street Journal also reported that the FDA's investigation is looking at the business of Kris Thorkelson, the Winnipeg-based owner of CanadaDrugs.com, an online pharmacy website that attracts international customers.

Haughton told the newspaper that Thorkelson is his brother-in-law.

Neither Haughton nor Thorkelson returned calls from CBC News on Wednesday.

CanadaDrugs.com issued a statement insisting it is not connected to the counterfeit Avastin case because the company doesn't sell that drug.

'Only a matter of time'

Some who have worked with Thorkelson said they have been worried for years about the potential of counterfeit drugs entering the pharmacy supply chain.

"It was inevitable. It was only a matter of time," said David Mackay, who has worked with Thorkelson at CanadaDrugs.com and is a former executive director of the Canadian International Pharmacy Association (CIPA).

"The supply chain has grown so vast and so convoluted, with so many countries, that the potential for counterfeit penetration just became that much more enhanced."

Daren Jorgenson, who was one of Thorkelson's first business partners in the internet pharmacy business, said he does not believe Thorkelson would have allowed the counterfeit drugs to be sold.

"If Kris knew there was a fake product in his distribution chain, he'd do everything in his power to shut it down and get it straight," Jorgenson said.

Jorgenson said he left the internet pharmacy industry after competitors began sourcing their drugs overseas.

"Everyone should always be concerned," he said. "There's no clear oversight on internet pharmacy products coming into the U.S."

With files from the CBC's Karen Pauls and The Associated Press