WASHINGTON (Reuters) - U.S. regulators may ask Congress to pass legislation to improve oversight of virtual currencies like bitcoin amid concerns about the risks posed by the emerging asset class, the head of the Securities and Exchange Commission said on Tuesday.

The comments by SEC Chairman Jay Clayton before the Senate Banking Committee are the strongest indication yet that federal authorities are mulling new laws to scrutinize virtual currency trading and investing.

Clayton, who testified alongside Christopher Giancarlo, chairman of the Commodity Futures Trading Commission (CFTC), said the agencies were coordinating with the Treasury Department and the Federal Reserve on the matter, but added that lawmakers may have to clarify and enhance regulatory powers.

“We may be back with our friends from Treasury and the Fed to ask for additional legislation,” Clayton said when asked whether Congress needed to act on virtual currencies.

The hearing followed a rout in the price of bitcoin, which has lost about half its value since the start of the year on concerns ranging from a global regulatory clampdown to a ban by some banks on using credit cards to buy bitcoin.

Senator Mike Crapo, the Republican chairman of the panel, and Democratic Senator Sherrod Brown were among the lawmakers to express worries about volatility, investor protections and the risks posed by cyber criminals in the virtual currency market.

“Between the enforcement actions brought by your agencies, the hack of the international Coincheck exchange...there is no shortage of examples that increase investor concerns,” Crapo said, referring to hackers’ recent theft of $530 million from Japanese bitcoin exchange Coincheck.

Bitcoin (virtual currency) coins are seen in an illustration picture taken at La Maison du Bitcoin in Paris, France, May 27, 2015. REUTERS/Benoit Tessier

Both Clayton and Giancarlo used the hearing to showcase the efforts their agencies have made to police the market and to highlight limitations in the current U.S. regulatory structure, whereby virtual currencies fall into a gray area between the SEC, CFTC, Treasury, the Fed and state regulators.

Federal legislation could help rationalize this patchwork and clarify which agency has the authority to police the underlying virtual currency cash market, the regulators said.

Giancarlo and Clayton warned, however, that while they had limited authority to write virtual currency rules, they would use their enforcement powers aggressively to protect investors from fraudsters.

Clayton repeated his position that public offerings comprising digital tokens, known as initial coin offerings (ICOs), are securities and subject to the same investor protection rules as equity market offerings.

The SEC will go after lawyers and firms that try to circumvent those rules, he said, although he did not clarify if the SEC would pursue ICOs that have already happened.

The CFTC is also working with the Federal Bureau of Investigation on money laundering and terrorist financing issues, Giancarlo said.

“As word is getting out that we will go after misconduct I think you’re starting to see that reflected in the price” of bitcoin, he added.

FUNDING ISSUES

The regulatory chiefs questioned how their respective agencies would fund increased scrutiny of the rapidly growing virtual currency market, with Clayton saying he needed more people to staff the trading and markets division.

“Personnel is my biggest challenge at the moment,” he added.

Committee members, however, did not appear to stake out a clear position on whether to pass virtual currency legislation.

Crapo noted that the underlying distributed ledger technology offered “present significant positive potential” to increase investor access to financial markets.

Democratic Senator Elizabeth Warren, a consumer advocate, also used the hearing as an opportunity to grill Clayton on other issues. These included reports the SEC is mulling rule changes that would block investors from being able to band together to sue companies, an idea Clayton said he personally is “not anxious” to pursue.

On the Luxembourg-based Bitstamp exchange, bitcoin hit $5,920 on Tuesday, its lowest since mid-November, before recovering to above $8,000 BTC=BTSP. It hit a high of $8,150 and was last at $7,922.79 in late trading in New York, up nearly 15 percent on the day.