A man has appeared at Bucharest Municipal Court, Romania, charged with producing and distributing indecent images of children and blackmail.
The charges are connected to a PSNI investigation into webcam blackmail linked to the death of 17-year-old Ronan Hughes in Co Tyrone in June 2015.
The 31-year-old has been remanded in custody.
PSNI have been liaising with a number of agencies in a variety of jurisdictions, including Policia Româna (Romanian Police), the Directorate for Investigating Organised Crime and Terrorism in Romania, the National Crime Agency, and Europol, as part of the investigation.
Detective Superintendent Gary Reid, from the PSNI's Reactive and Organised Crime Branch, said: "Detectives from the PSNI are currently in Romania assisting our colleagues with this phase of the investigation.
"This has been complex and protracted and we are grateful to our colleagues in our partner agencies for their assistance to date.
"As legal proceedings are now ongoing, it would be inappropriate to comment further at this stage.
"However, I would like to take this opportunity to remind everyone in Northern Ireland to be mindful of their online activity, particularly with strangers. If you feel you have been compromised online in anyway, please report it to police on 101 or 999 in an emergency.
"We understand the level of media interest in this development however we are in close contact with the Hughes family and they have asked us to remind all media that they do not wish to be contacted at this time. I would ask you to respect their wishes."
At the time of Ronan's tragic death in 2015, parish priest Fr Benny Fee, said the close-knit rural community had been left stunned.
Fr Fee blamed "faceless individuals" for intimidating the teenager, saying: "He did not take his own life. His life was taken by these faceless people who put the child into a burning building that he felt he could not escape."
It is understood Ronan had told his parents about the cyber-bullying and made a complaint to police.
Fr Fee added: "It is a total and absolute tragedy but it is a different kind of tragedy because there is an element of cyber-crime involved. It is just so tragic that these faceless people have robbed a family and community of a much-loved child."