AlphaBay and Hansa, two of the Dark web’s largest markets, were taken down as part of a joint effort involving multiple law enforcement agencies. Authorities claim to have collected user data from the sites, used for the sale of illegal drugs and firearms.

“This is likely one of the most important criminal investigations of the year – taking down the largest dark net marketplace in history,” US Attorney General Jeff Sessions said in a press conference, claiming that “American people are safer,” following the operation.

At the DOJ news conference, an official with the Drug Enforcement Administration said the site fed the opioid epidemic in the US by “supplying countless addicts with direct sales.”

Msg on dark web site for #Hansamarket taken down in joint international effort pic.twitter.com/hBbgaVQ3hT — Colm McGlinchey (@ColmMcGlinchey) July 20, 2017

The operation was led by the United States but involved cooperation among international law enforcement in Thailand, the Netherlands, Lithuania, Canada, the United Kingdom, and France, as well as the European police agency. Europol.

At the time of its takedown AlphaBay, which had been in operation for over two years, had more than 250,000 listings for illegal drugs and toxic chemicals, and more than 100,000 listings for stolen and fraudulent identification documents, hacking tools and firearms, according to Europol.

#BREAKING Largest criminal marketplaces on the DarkWeb -AlphaBay & Hansa- shut down in global law enforcement action https://t.co/A1kyA78v6upic.twitter.com/CsYc9ymnIO — Europol (@Europol) July 20, 2017

Rob Wainwright, the Executive Director of Europol, described the takedown as a “serious hit” to drug traffickers and “other serious criminals around the world,” in a statement. “There are more of these operations to come,” he warned.

As part of the operation, Dutch police took control of Hansa after it was seized in June. It remained in operation, while displaced users from the AlphaBay shutdown earlier this month migrated to Hansa.

“In fact they flocked to Hansa in their droves, with an eight-fold increase in the number of new members of Hansa recorded immediately following the shutdown of AlphaBay,” according to Europol.

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This allowed Dutch police to monitor the activity of users without their knowledge. Some 10,000 addresses of European Hansa customers were collected over the course of the investigation, according to Europol.

Both markets are accessible via the Tor browser, used to access the dark web.

Earlier this month 26-year-old Canadian citizen Alexandre Cazes was arrested in Bangkok on suspicion of being one of AlphaBay’s operators. He was awaiting extradition to the US when, on July 12, he was found hanged in his jail cell, reported the Bangkok Post.