WASHINGTON — Sens. Sherrod Brown, D-Ohio, and Elizabeth Warren, D-Mass., sent a letter to the Treasury Department on Thursday urging an investigation into whether any U.S. or U.S.-linked entities are associated with the Panama-based law firm Mossack Fonseca & Co. and its schemes to help wealthy individuals and businesses evade taxes and launder money.

Since it is "the primary agency charged with protecting the integrity of the U.S. financial system and enforcing our laws against money laundering and terrorist financing, we strongly urge the Treasury Department to conduct its own inquiry into Mossack Fonseca's activities and its clients," Warren and Brown wrote.

The lawmakers also asked Treasury to look into whether any of the entities or individuals involved with the firm have helped specially designated nationals on the Office of Foreign Assets Control to launder money. U.S. entities or people are not allowed to do business with those banned on the OFAC list.

The Department of Justice is reportedly looking into the law firm's leaked documents known as the "Panama Papers," but the lawmakers are asking Treasury to do a separate review. News outlets that have had access to leaked documents have reported that more names will be released including those with ties to the U.S.

Five hundred banks and their subsidiaries, including UBS and HSBC, have already been named in having helped clients of Mossack Fonseca to set up offshore "shell" companies.

"These disturbing revelations and others reveal activity that may threaten our national security and our financial system by undermining U.S. and international laws promoting financial transparency and combating money laundering and terrorist financing," Brown and Warren wrote.

"The reported involvement of U.S. or U.S.-linked institutions and individuals in what may have been efforts to enable international money laundering and tax evasion raises important questions about the susceptibility of the U.S. financial system to money laundering, terrorist financing, and other illicit enterprises."

Brown and Warren also said the revelation underscores the need to confirm Adam Szubin as undersecretary for terrorism and financial intelligence.

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