Spanish national police dismantled the largest international child pornography distribution network to date though pioneering research examining instant messaging groups and WhatsApp messages.

The operation monitored 135 users in 18 countries in Europe, Central America and South America who participated in some 96 online pedophile groups.

A total of 39 people have been arrested: 17 of them in Spain, six in Colombia, four in Italy, two in Germany, three in Bolivia, two in Costa Rica, two in Paraguay, one in Chile, one in El Salvador and one in Portugal

The operation was carried out by the Technological Investigation Unit of the Spanish National Police and coordinated by Europol and Interpol, reported Spanish police today.

The groups shared files that included scenes of humiliating treatment and excessive brutality of young children.

Some of the files discovered in the operation include encounters with minors that date back twenty years.

This is the first joint international action against child pornography in the European Union to be coordinated through the Action Group Against Cybercrimes in The Hague, said Spanish police in a statement.

The investigation was initiated in June 2016 by Spain’s Technological Research Unit following the detection of a link in the TOR (The Onion Router) network – a set of servers that allows users to anonymize their IP.

Investigators infiltrated the networks by being invited to participate in chat groups dedicated to exchanging child pornography. They were given a URL which redirected them to a repository which gave information on how to access, through anonymous networks, instant messenger services run by pedophiles. Spanish investigators identified a large number of groups dedicated to distributing child porn on WhatsApp.

Researchers were shocked to wind up finding over 360,000 files with graphic images of child pornography that depicted sexual exploitation of children, and humiliating and degrading treatment inflicted on minors between the ages of zero and eight.

The operation, in addition to the arrests in many countries, also lead to the seizure of various electronic devices from 19 houses including 23 mobile phones, seven laptops, a tablet, three cameras, ten external hard drives, ten pendrives, nine large capacity SD storage cards and 64 DVDs, reported Spanish police.