United Brotherhood, an organised crime group, is masterminding an extensive drug trafficking operation in Finland's prisons, reports the news syndicate Lännen Media.
The gang has been investigated for extortion, and drug and gun offences in the past.
Authorities interviewed by the syndicate say there are also signs that violence in Finland's prisons in on the rise and has escalated. Some prisoners are pressured into smuggling drugs into the prison after home leaves, while others are forced to pay fees and penalties.
The investigation found that the gang also took advantage of prison staff to run the operation.
Detective chief inspector Christer Ahlgren from the National Bureau of Investigation said in an interview that the situation is serious, as the United Brotherhood is considered one of the most dangerous organised crime groups in Finland due to the number of violent crimes for which it has been investigated.
Lännen Media reports that the gang is behind several aggravated cases of assault that have taken place at the Riihimäki prison this year.