FORTUNE — European Union regulators have filed formal charges against three banks over the alleged operation of an illegal cartel to rig interest rates.

The banks in question — Credit Agricole CRARY , HSBC HSBC , and JPMorgan JPM — are facing EU charges, but they are not the only banks implicated in the scandal, reports the Wall Street Journal.

Four other banks — Barclays BCS , Deutsche Bank DB , RBS RBS , and Societe Generale SCGLY — have all admitted they were involved in the cartel, and so had their penalties reduced by 10% as part of a settlement with the EU last December, the Journal said.

This case also comes five months after the EU fined six banks €1.71 billion ($2.3 billion) for colluding to set benchmark interest rates.

The banks could face fines of 10% of their worldwide turnover if found guilty.