After a yearlong sting operation, US law enforcement officials have arrested 35 people suspected of selling "illicit goods" on the darknet, the Justice Department said Tuesday.

The operation, which included the Secret Service, the Drug Enforcement Administration and the Postal Inspection Service, was the nation's "first nationwide undercover operation targeting darknet vendors," the Justice Department said in a statement. The darknet is a part of the web that can be accessed only through specific software and a dedicated browser, such as the Tor Project's browser, which hides users' online identities.

In addition to the arrests, the operation resulted in the seizure of illegal narcotics, firearms, $3.6 million in cash and gold bars, and nearly 2,000 Bitcoins and other cryptocurrencies with an approximate value of $20 million, the Justice Department said.

"The Darknet is ever-changing and increasingly more intricate, making locating and targeting those selling illicit items on this platform more complicated," Derek Benner, executive associate director of US Immigration and Customs Enforcement's Homeland Security Investigations (HSI), said in a statement. "But in this case, HSI special agents were able to walk amongst those in the cyber underworld to find those vendors who sell highly addictive drugs for a profit."

The Justice Department said agents posed as money launderers on Darknet market sites, exchanging US currency for virtual currency. This operation led agents to vendors of illicit goods and the creation of more than 90 active legal cases around the country, the Justice Department said.

Among the items seized during a four-week police action at the end of the investigation were 333 bottles of liquid synthetic opioids, computer equipment for mining bitcoin, and a grenade launcher.

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