Dutch detectives have gained access to 3.6 million encrypted emails sent by criminal gangs which will be used in dozens of prosecutions, the public prosecution department said on Thursday.

The information in the mails will provide evidence for criminal cases, including murder, armed robbery, drugs, money laundering and other forms of organised crime, the department said in a statement.

The messages were found on servers in Canada belonging to a Dutch company called Ennetcom. Last year, the public prosecution department won the right to have the Ennetcom servers copied and the seven terabytes of information sent to the Netherlands for investigation.

Ennetcom was the ‘biggest provider of encrypted communications in the Netherlands’, the department said. The company also has sales points in South America and other countries in western Europe.

The owner of Ennetcom was arrested last April when the network was shut down as part of the investigation. He has since been released from jail but is facing prosecution.

The major police investigation into Ennetcom stems from other investigations into the recent spate of gangland killings in the Netherlands. Detectives found that many of those involved had encrypted Ennetcom telephones in their possession.