More than 10 people are facing charges after a four-year cross-border probe into the "highest level" of traditional organized crime – an investigation that resulted in the seizure of mass quantities of illicit drugs, including the deadly opioids fentanyl and carfentanil.

The seizures and arrests come amid a growing opioid crisis in Canada that is costing thousands of lives a year from overdoses.

Project OTremens, led by the RCMP's Greater Toronto Area Combined Forces Special Enforcement Unit with support from local and provincial police services, began in 2013 when officers encountered an opportunity to infiltrate some of the "higher echelons" of organized crime.

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On Thursday, four years later, more than 100 police officers executed search warrants at more than a dozen residences and businesses in Southern Ontario, Montreal and Vancouver.

Nine people have been charged with 75 offences including conspiracy to traffic fentanyl and carfentanil; trafficking fentanyl, carfentanil and heroin; conspiracy to import and traffic cocaine; trafficking cocaine; trafficking methamphetamine, MDMA, MDA and LSD; weapons trafficking; trafficking of contraband tobacco; and bookmaking.

Canadawide warrants have been issued for another five people.

One of the most lauded seizures in the OTremens investigation was the undercover purchase of six kilograms of fentanyl and carfentanil – a deadly volume as mere grains of the opioid are enough to be lethal.

The interception came the same week that Toronto opened its first permanent supervised drug-consumption site – a local response to the opioid crisis that claimed the lives of more than 2,800 Canadians last year.

A continuing Globe and Mail investigation found that the federal and provincial governments did not do enough to stop the overprescribing of powerful painkillers such as oxycodone, hydromorphone and fentanyl. The crisis has only deepened with the arrival of illicit fentanyl and the even deadlier carfentanil.

While RCMP Superintendent Chris Leather says this investigation has put a "dent" in that illicit market, he cautions that the drug trade is constantly evolving.

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"Even as police crack down on fentanyl, more powerful substitutes are beginning to appear. Shipments of carfentanil and W18, both 100 times stronger than fentanyl, have recently been seized by police in Canada," he said.

Among those from Ontario facing charges in this case, Supt. Leather said, are "well-known organized crime members" including Domenico Violi and Giuseppe Violi of Hamilton, Massimigliano Carfagna of Burlington, Adriano Valentino Scolieri of Richmond Hill and Wojciech Grzesiowki of Innisfil.

The RCMP also confirmed Thursday that the OPP's arrests of Giovanni Commisso and Jing Git Wong last month – charged in Vaughan with trafficking contraband tobacco – were linked to Project OTremens.

Across the border, in a parallel but separate investigation by the Federal Bureau of Investigation into the Cosa Nostra in New York, Special Agent Michael McGarrity said Thursday that alleged members and associates of the Gambino and Bonanno crime families were picked up and charged with cocaine trafficking, loan sharking, extortion and money laundering.

Named in the New York indictment are Paul Semplice, "a member of the Gambino crime family," Salvatore Russo, "an associate of the Bonanno crime family," Damiano Zummo, "an acting captain in the Bonanno crime family," and Paul Ragusa, "an associate of the Bonanno and Gambino families" and – according to Mr. McGarrity – "a former FBI Top 10 fugitive."

In addition to assistance from local police and international RCMP liaison officers, the service also had support from international agencies including the U.S. Department of Homeland Security, the Colombian National Police and multiple Italian police departments.

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Police say Project OTremens also highlighted organized crime's ability "to corrupt people in positions of public trust."

During their investigation, they say, it came to light that a Toronto Police Service employee was allegedly making database queries on behalf of a criminal organization involving one of the accused. Erin Maranan has been charged with 20 counts of breach of trust.

In addition to the fentanyl and carfentanil seizures, Supt. Leather said officers seized more than a kilogram of heroin, more than 20 kilograms of cocaine, more than 250,000 ecstasy tablets, approximately three million unstamped cigarettes, luxury vehicles and several gambling machines. Police said the fentanyl and carfentanil seized, after dilution, would have meant three times as much would have made its way on to the streets.

It is a "significant dent," Supt. Leather said. "For the time being, at least it will have significant impact."