JPMorgan Chase, HSBC Holdings and Credit Agricole were fined a total of 485.5 million euros ($521 million) for rigging the Euribor benchmark as European Union antitrust regulators wrapped up a five-year investigation into the scandal.

The trio colluded to rig the Euribor rate and exchanged sensitive information to suit their trading positions in correlated derivatives markets, in breach of EU antitrust rules, the European Commission said on Wednesday in an e-mailed statement. JPMorgan was fined 337.2 million euros ($362 million), HSBC got a 33.6 million-euro penalty and Credit Agricole must pay 114.7 million euros.

"The participation in such schemes was very lucrative for the banks," Margrethe Vestager, the EU's antitrust commissioner, told journalists in Brussels, adding that it's very difficult to make an exact estimate of their profits. "Tiny movements of the Euribor rate can have a huge impact given the trading volumes at stake."

The EU's investigation into Euribor manipulation was strained three years ago after Credit Agricole, JPMorgan and HSBC refused to join a multibank settlement with four other lenders including Deutsche Bank AG and Societe Generale SA. Since then, the holdouts have been a thorn in the commission's side -- successfully delaying the process and showing up the regulator for its handling of the case.

JPMorgan "did not engage in any wrongdoing with respect to the Euribor benchmark," Jennifer Zuccarelli, a spokeswoman for the bank in London, said in a statement. "We will continue to vigorously defend our position against these allegations, including through possible appeals to the European courts."

Credit Agricole in a statement said it "firmly believes that it did not infringe competition law" and that "it will appeal the commission's decision." The fine payment "will not affect the 2016 financial statements given the provisions set aside previously," the Montrouge, France-based bank said.

HSBC said it "did not participate in an anti-competitive cartel," and is also considering its legal options, according to a statement.

The four banks that settled the Euribor case were accused of sharing, via phone and through online chats, sensitive trading information among themselves and strategizing to push benchmark rates up or down to suit their trading positions.

Vestager said traders at all seven banks involved regularly used "vulgar language" in their interactions, which required "a kind of dictionary" to make sure the evidence wasn't lost in translation.

"I think I would be seriously blushing if I were to repeat any of the wording in some of those chat rooms," she said.

The trio of holdouts were handed a statement of objections in May 2014 accusing them of colluding to rig Euribor rates in the wake of a global scandal embroiling some of the world's biggest banks. By refusing to settle the case with the commission they forfeited the chance of a 10 percent discount on any fines.

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