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(Reuters) - Visa Inc V.N on Thursday said the Federal Trade Commision (FTC) has initiated an inquiry into whether the payments processor's actions prohibited merchants from using other debit payment networks.

Bloomberg Law reported here on Wednesday the regulator was investigating whether Visa and rival Mastercard Inc M.N blocked retailers from routing card transactions over alternative networks such as Pulse, NYCE and Star.

Visa in a regulatory filing bit.ly/2Xdju7s said it received a letter from the FTC on Nov. 4, and the company is cooperating with the bureau.

Mastercard did not immediately respond to a Reuters request for comment on Thursday.

The inquiry could spell fresh trouble for the world’s two largest payments processors which settled a European Union antitrust probe in April this year over card fees.