Spanish competition regulators opened a probe into four Spanish lenders, including Banco Santander SA, over possible collusion on setting prices for interest-rate derivatives.

The proceeding relates to fixing prices and the possible exchange of sensitive commercial information relating to derivatives used as as part of syndicated loans, the CNMC regulator said Thursday in an e-mailed statement. Banco Bilbao Vizcaya Argentaria SA, CaixaBank SA and Banco de Sabadell SA are also being investigated. The probe comes after a complaint was filed, the CNMC said.

BBVA is certain it has acted according to the law, an official for the bank said. Officials for Santander and CaixaBank declined to comment. Sabadell officials couldn’t immediately be reached for comment.

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