Main Street investors buying bitcoin and other cryptocurrencies think those markets are regulated just like a stock exchange, two regulators told the Senate Banking Committee on Tuesday.

They're not. And addressing the gap in a way that protects average Americans may require Congress to pass new legislation giving regulators additional authority, Securities and Exchange Commission Chairman Jay Clayton and Commodity Futures Trading Commission Chairman J. Christopher Giancarlo said.

A patchwork of existing federal and state laws covers pieces of cryptocurrency markets, "but there's not a comprehensive structure," Giancarlo said. "That's something I think is a policy discussion, an important one, to be had."

The so-called spot markets for cryptocurrencies, real-time sales of bitcoin and ethereum, are unregulated, Giancarlo said, though his agency has oversight of futures contracts based on them. The SEC's authority, meanwhile, covers "initial coin offerings" that introduce new forms of virtual currency and won a court order in late January halting one it claimed was fraudulent.

Both Clayton and Giancarlo are appointees of President Trump, who has advocated looser regulations to boost economic growth as long as adequate safeguards are maintained. Their assessment followed testimony from Treasury Secretary Steve Mnuchin, who told senators in late January that it's important to ensure consumers tempted by run-ups in prices — bitcoin surged 14-fold last year — are aware of the risks.

Cryptocurrencies are generated, or mined, when networked computers record and validate transactions in blockchain, a secure ledger accessible worldwide by multiple parties. Not only are the prices volatile, digital currencies are used in a variety of crimes including ransomware attacks, and transactions in them are largely untraceable.

Corporate titans from Warren Buffett to JPMorgan Chase's Jamie Dimon have both shunned doing business in cryptocurrencies, with Dimon suggesting that governments will begin to crack down if they grow large enough to affect nations' ability to control their money supplies.

"Many promoters of initial coin offerings and cryptocurrencies are not complying with our securities laws and, as a result, the risks are significant," Clayton said in prepared testimony. "There are significant security risks that can arise by transacting in these markets, including the loss of investment and personal information due to hacks of online trading platforms and individual digital asset 'wallets.'"

He and Giancarlo concurred with a suggestion from Sen. Mike Crapo, an Idaho Republican, that U.S. regulators should assess what authorities they already have to regulate cryptocurrencies and what additional tools Congress should provide them.

Already, the Financial Stability Oversight Council, a group of regulators that Mnuchin chairs, has set up a working group on virtual currencies.

At the same time, maintaining perspective on the potential risk is important, Giancarlo noted. As of Monday, the value of outstanding Bitcoin was about $130 billion, and that of all cryptocurrencies combined was about $365 billion.

That's lower than the $800 billion market value of iPhone maker Apple, the $2 trillion in assets held by San Francisco-based lender Wells Fargo or the $15 trillion U.S. mortgage market prior to the 2008 financial crisis.