Two members of the United States Senate have called on the heads of federal financial regulators to address “ties between the banking industry and cryptocurrency firms” in the wake of FTX’s collapse.

In letters dated Dec. 7 to Federal Reserve chair Jerome Powell, acting Comptroller of the Currency Michael Hsu, and Federal Deposit Insurance Corporation acting chair Martin Gruenberg, Senators Elizabeth Warren and Tina Smith — both on the Senate Banking Committee — acknowledged that the crypto industry was not so “deeply integrated” with traditional financial institutions to severely impact markets after FTX’s bankruptcy filing. However, the two lawmakers pointed to reports suggesting ties between FTX and the Washington-based Moonstone Bank as well as stablecoin issuer Tether and the Bahamas-based Deltec Bank with seemingly no oversight from federal regulators.

The senators called on Powell, Hsu, and Gruenberg to provide information on whether the regulators planned to review crypto firms’ connections to banks, as well as a list of banks regulated by the agencies currently engaged in crypto-related activities. In addition, Warren and Smith questioned the heads as to whether FTX may have used customer funds to invest more than $11 million in Moonstone, setting a Dec. 21 deadline for answers.