A year-long undercover operation for vendors selling 'illicit goods' on the internet ended this month with the arrests of more than 35 people and the seizure of millions of dollars worth of drugs, guns and Bitcoin.

The Department of Justice announced the news in a press release on Tuesday saying that the operation, which targeted darknet vendors, was 'the first nationwide undercover action' of its kind.

The operation involved the Secret Service, the Drug Enforcement Administration, Homeland Security Investigations and the Postal Inspection Service.

40 vendors of 'illicit goods' were arrested across the country in a year-long undercover operation, the Department of Justice said

Feds also seized millions of dollars worth of drugs, including Xanax,Oxycodone, MDMA, cocaine, LSD and marijuana

The DoJ said Homeland Security Investigations agents from New York posed as money launders during the operation

More than 100 weapons, including guns and a grenade launcher, were also seized by the authorities

The Department of Justice said that HSI agents from New York posed as money launderers on darknet market sites, a part of the web that can only be accessed through specific software and a dedicated browser that hides users' online identities.

The undercover agents exchanged hard currency for virtual currency, which led them to 'numerous vendors of illicit goods'.

The operation led to the arrests of 40 vendors across the country and the seizure of more than 100 guns, more than $20million in Bitcoin, $3.6million in US currency and gold bars, as well as prescription pills and drugs such as Xanax,Oxycodone, MDMA, cocaine, LSD and marijuana.

A grenade launcher and 333 bottles of liquid synthetic opioids were also seized.

$3.6million in US currency and gold bars were seized, as well as more than $20million in Bitcoin

Dozens of cases have been opened against vendors since the operation, and more than 90 cases are now active

Officials said the investigation is ongoing. Federal authorities are seen above removing items

Dozens of cases have been opened against vendors since the operation, and more than 90 cases are now active.

'The Darknet is ever-changing and increasingly more intricate, making locating and targeting those selling illicit items on this platform more complicated, acting HSI Executive Associate Director Benner said in the press release.

'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 investigation is ongoing.