Properties linked to an organised crime group responsible for selling MDMA on the dark web have been raided by officers from the UK's National Crime Agency and US Homeland Security.
Two men, aged 24 and 31, were arrested during the raids on Thursday, one in South Shields and another in Hebburn, while two others remain on the run and are believed to be overseas.
It is the latest action following the international effort to infiltrate the EncroChat phone network and came as authorities captured a drugs haul with a combined street value of £4.3m, the NCA said.
According to the authorities, EncroChat messages - thought by criminals to be encrypted and secure from police - allowed officers to identify individuals involved in supplying drugs and laundering the proceeds using cryptocurrency.
During the raids on 1 April, officers seized mobile phones, computers and drug packaging paraphernalia, although no drugs were recovered.
One of the group's members, Mubinar Rahman, aged 25, from South Shields, was arrested last July. He has since admitted posting over 100 packages and is due to be sentenced on 21 April at Newcastle Crown Court.
At the time of Rahman's arrest, the NCA recovered a total 90 kilos of MDMA, 134 kilos of amphetamine and more than 6,000 diazepam/alprazolam tablets.
The drugs were being imported to the UK from the Netherlands and then sold on the dark web using four handles - HundredsUK, Hundredsandthousands, Sundaefundae, and 100and1000s.
Packages of MDMA were intercepted by the NCA and Border Force last summer destined for addresses in the UK, America, Israel, Norway, Thailand, Hong Kong and Kuala Lumpur.
NCA Operations Manager Martin Clarke said: "This action against an organised crime group supplying drugs via the dark web has dismantled a well-established operation.
"We have worked closely with partners in the US to target the individuals involved, who are ultimately preying on the vulnerable and destroying communities.
"This investigation shows that those who try to use the dark web and encrypted communication devices to anonymously commit crimes can be identified.
"There are two people from South Shields we are still seeking, who we believe are overseas. They know they are wanted, and I would encourage them to hand themselves in," Mr Clarke added.
Eric Felman, the US Homeland Security Investigations attache, said: "One of our top priorities as an agency is to disrupt and dismantle international narcotic smuggling activities at home and around the globe.
"The strong partnership between Homeland Security Investigations and the National Crime Agency continues to produce positive results in combatting organised international crime affecting both of our countries."