Photo

Authorities around the world are grappling with how to regulate virtual currency in the wake of the implosion of Mt. Gox, a prominent trading platform for Bitcoin.

In Tokyo, where Mt. Gox is based, Japan’s top government spokesman, Yoshihide Suga, said on Wednesday that agencies including the Financial Services Agency, the Finance Ministry and the police were collecting information on the Bitcoin trade in Japan, with an eye toward regulatory action.

“Once we assess the situation, we will respond as necessary,” Mr. Suga told a news conference. “At the moment, we are still in the information-gathering stage.”

Japan’s new interest in Bitcoin came as authorities elsewhere were taking steps.

In the weeks before the collapse of Mt. Gox, federal prosecutors in Manhattan sent a grand jury subpoena to the company, according to people briefed on the matter. The prosecutors, who had already criminally charged the founder of a popular website where Bitcoins could be bought, have formed a broader partnership with the Internal Revenue Service and other federal agencies to crack down on companies using Bitcoin exchanges to filter tainted money and support drug trafficking.

New York State’s top financial regulator, Benjamin M. Lawsky, has also signaled an interest in regulating the virtual currency. And the Commodity Futures Trading Commission is examining its potential authority over Bitcoin exchanges that have a United States presence, a person briefed on the matter said, as is the F.B.I. in New York.

Mt. Gox — its name is derived from Magic the Gathering Online Exchange, showing its origins as a gaming platform — was one of the earliest Bitcoin exchanges. It stopped trading on Monday after having halted user withdrawals earlier. An unverified document that circulated on the Internet Monday night pegged Mt. Gox’s losses at 744,000 Bitcoins, or 6 percent of the 12.4 million Bitcoins currently in circulation.

Yet the shutdown has not curbed enthusiasm for the virtual currency. The price of Bitcoin rose about 8 percent on Wednesday, to $577, according to the virtual-currency monitoring site CoinDesk.

Shortly before going offline, Bitcoins were trading on Mt. Gox at just over 20 percent of what they were selling for elsewhere.

“There were a lot of people who were trying to buy Bitcoin at what appeared to be discounted prices,” said Gil Luria, a managing director at Wedbush Securities. “A lot of the demand was going to Mt. Gox, and once Mt. Gox completely shut down, that level came back into all the other exchanges.”

Another large Bitcoin exchange, BTC-e in Bulgaria, posted a notice on Tuesday saying that it would have to move to a new platform “in order to cope with an increased number of client requests.”

“It seems like it should be panic, but the reality on the ground is it’s really not,” said Fred Ehrsam, co-founder and president of Coinbase, which facilitates Bitcoin transactions.

In a statement on Mt. Gox’s website on Wednesday, its chief executive, Mark Karpeles, said he was still in Japan and “working very hard with the support of different parties to find a solution to our recent issues.”

He also said that Mt. Gox employees had been instructed not to give out any information and asked users to refrain from asking the staff questions.

Like their counterparts elsewhere, Japanese authorities are heading into unfamiliar territory in regulating a virtual currency.

A relatively easy regulatory change would be to bring Bitcoin under the purview of Japan’s Payment Services Act, which oversees electronic money, shopping points and escrow transactions. That could enforce new limits on Bitcoin transactions, including their size.

While Bitcoin has faced relatively little scrutiny in Japan, it has invited comparisons to an infamous scandal involving Enten, an electronic currency used by a Tokyo company to defraud investors of billions of yen in the mid-2000s.

Bitcoin was created in 2009 by an anonymous programmer or collective of programmers known as Satoshi Nakamoto. Attracted to the promise of lower transaction costs and a currency that could circumvent the traditional banking system, Bitcoin initially attracted a loyal following of technology aficionados, entrepreneurs and those with libertarian or anti-establishment leanings.

Since then, more established players have come on board, including Marc Andreessen, who has invested in Coinbase, the brothers Cameron and Tyler Winklevoss, who own about $64.1 million in Bitcoin, and Fred Wilson, a partner in the investment firm Union Square Ventures.

All of those investors have voiced their support of Bitcoin in recent days.

“I will happily retweet all retractions and apologies from people who wrongly forecasted death of Bitcoin as result of Mt. Gox collapse,” Mr. Andreessen posted on Twitter on Wednesday.

Ben Protess and Zhiyi Yang contributed reporting.