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Southern police have confirmed they are aware of Facebook groups dealing in illegal drugs and have used information gleaned to help deter the operations.
The confirmation follows news Canterbury police have been monitoring social media pages involved in the black market and, in some cases, sending letters to members warning them they are being watched.
Detective Senior Sergeant Malcolm Inglis said police were aware of online black market groups in the Southern District.
They had visited group members to warn them of the consequences and would continue to do so.
''Generally, if we're aware of people doing importations, if they're not of a major scale, we'll go and visit them and warn them about what they're getting into.''
Sending letters was not out of the question, Det Snr Sgt Inglis said.
''We definitely would [consider it].
''It's not a bad option, but at this stage we'll front up and just let them know that we're aware of it.
''But letters are certainly within the scope of things we could use.''
The police national cybercrime centre had issued a directive that all police be trained in fighting cybercrime by 2017 as the online market expanded.
Det Snr Sgt Inglis said younger officers in the district had helped with identifying online threats.
''We've got some good young staff who are certainly better than I am,'' he said.
''They've grown up with the internet and Facebook and all of those changes which can be used to facilitate importation of drugs through the black market.
''There are all sorts of things that can be imported through the black web - explosives, guns, drugs.
''It's a pretty dangerous environment, really, and one we've all got to be aware of.''