The head of the powerful U.S. Senate banking committee sent letters to stablecoin issuers and exchanges seeking information on how companies are protecting consumers and investors amid the risks highlighted in the recent report by the President’s Working Group on Financial Markets.

Sen. Sherrod Brown, Chair of the U.S. Senate Committee on Banking, Housing, and Urban Affairs, said consumers and investors may not understand how stablecoins work and the risks involved.

“I have significant concerns with the non-standardized terms applicable to redemption of particular stablecoins, how those terms differ from traditional assets, and how those terms may not be consistent across digital asset trading platforms,” wrote Sen. Brown in his letter to Circle, the payment services company that operates stablecoin USD coin (USDC)

Brown also sent letters to cryptocurrency exchanges Coinbase, Gemini, Binance.US as well as blockchain infrastructure firm Paxos, which operates the Pax dollar stablecoin, decentralized finance company TrustToken, which operates the TUSD stablecoin, and Centre, the Coinbase- and Circle-founded project that oversees the USDC stablecoin.

The report compiled by the President’s Working Group, along with the Federal Deposit Insurance Corporation and the Office of the Comptroller of the Currency, is the first step toward establishing federal-level regulatory oversight of the stablecoin sector in the U.S.

The regulators behind the report called on Congress to bring stablecoins under federal supervision. The report indicated that should lawmakers fail to do so, the regulators themselves may step in through the interagency Financial Stability Oversight Council (FSOC), which could designate stablecoin activities “systemically important” and thus subject to tighter supervision.

Stablecoins are cryptocurrencies tethered 1:1 to the value of other assets like the U.S. dollar, and issuers maintain the fixed value of these currencies by backing them with reserves that match the value of the coins in circulation. This year, Tether, issuer of USDT, revealed that about 50% of its reserves were made up of unspecified commercial paper.

Last month, Circle disclosed it was under investigation by the U.S. Securities and Exchange Committee (SEC). Tether may also be under the SEC’s microscope. Meanwhile, Europe is gearing up to approve a 168-page framework to regulate crypto, which proposes additional standards for major stablecoin issuers in particular.

Read also: US Stablecoin Report Gets Mixed Reviews From Crypto Industry