Senator Elizabeth Warren (D-MA) addresses the audience at the morning plenary session at the Netroots Nation conference for political progressives in Atlanta, Georgia, U.S. August 12, 2017. REUTERS/Christopher Aluka Berry

WASHINGTON (Reuters) - A decision by Mitsubishi UFJ Financial Group Inc (MUFG) to shift its U.S. banks from state regulators to a federal bank regulator is garnering scrutiny from a pair of U.S. Democratic senators.

Senators Elizabeth Warren and Chris Van Hollen sent a letter to the Office of the Comptroller of the Currency on Monday, pressing for details on the regulator’s decision to allow the bank to come under its purview, after it had sparred with New York’s banking regulator.

Earlier this month, MUFG’s Bank of Tokyo-Mitsubishi UFJ Ltd branches in New York, Illinois, Texas and California were granted federal charters, allowing the bank to be regulated by the Trump administration rather than state governments.

The pair said they were “disturbed” by the decision, and questioned whether the shift to a federal banking license allowed the bank to escape any investigations by the New York Department of Financial Supervision, where the company had bank branches.

They also questioned the role of Acting Comptroller Keith Noreika, who previously counted MUFG as a client, in the decision. Noreika recused himself from the bank’s application for a federal charter, but the two senators are demanding additional details on that decision, and who was responsible for approving the bank’s charter instead.

An OCC spokesman did not immediately respond to a request for comment.