Senator Elizabeth Warren (D-Mass.) on Tuesday questioned the Office of the Comptroller of the Currency letting nine crypto firms operate as banks without proper safeguards.

The Senate Banking Committee's top Democrat sent a letter to the Office of the Comptroller of the Currency questioning the charters of nine crypto firms.

Last year, the OCC granted conditional approvals to Circle, Ripple, BitGo, Fidelity, and Paxos, as well as other firms more recently.