U.S. officials are investigating possible violations of sanctions against Iran by Royal Bank of Scotland, Britain's Financial Times reports.

The bank declined to comment on Wednesday's report except to repeat previous disclosures that it is in contact with U.S. and British authorities "to discuss its historical compliance with applicable laws and regulations, including U.S. economic sanctions regulations."

The Financial Times says the U.S. Department of Justice and the Federal Reserve investigations were prompted by voluntary disclosures made by the bank about 18 months ago.

Two years ago, Royal Bank of Scotland was fined $500 million by U.S. regulators for money-laundering activities by the Dutch bank ABN Amro, which was taken over in 2007 by a consortium led by RBS.