The European Commission has fined Credit Agricole, HSBC and JPMorgan Chase a total of €485 million  ($520 million) for their alleged participation in a cartel to manipulate the price of the Euribor financial benchmark. JPMorgan Chase got the largest fine - €337 million.

According to the EU, the trio were part of a 7-bank cartel that colluded between September 2005 and May 2008 to distort the Euribor interest rate which was set using quotes submitted by a panel of banks and is widely used in international money markets. Deutsche Bank, RBS and Societe Generale admitted guilt in December 2013 and were fined 825 million euros. Barclays avoided a penalty because it alerted the Commission.

The Commission found a series of chatroom messages between the traders at the banks congratulating each other on their actions.

"On days when traders received money calculated on the basis of Euribor, (they) had an interest in a high Euribor rate. On days when a trader needed to pay ... he would want to have a low Euribor rate," EU competition commissioner Margrethe Vestager said.

"The participation in such schemes was very lucrative for the banks ... tiny, tiny movements in the Euribor rate can have a huge impact because of the volumes of trading," she added.

Prosecutors have also charged more than a dozen men with fraud-related offences.