Manhattan US attorney Preet Bharara’s office is seeking information from businesses dealing in bitcoin on how some of them handled cyber-attacks that hamstrung several exchanges in recent weeks, a source familiar with the probe told Reuters on Wednesday.

Subpoenas have been sent to numerous businesses, including MtGox, once the largest bitcoin exchange, as well as other firms that did business with the Tokyo-based company, the source said.

Prosecutors want to know more about the nature of the cyber-attacks on MtGox and other exchanges and how those exchanges dealt with them. MtGox halted customer withdrawals on 7 February in response to what it termed unusual activity, and on Tuesday the exchange went dark, leaving customers unable to recover their funds.



Mark Williams, a risk management expert who teaches finance at Boston University, said the investigation is a positive step in regulating virtual currency.

“If bitcoin is going to be a currency then it needs to actually play by the rules,” Williams said. “At this point, there’s been no regulation in this sector.”



Regulators have faced some hurdles in regulating bitcoin, which has not been designated as a currency or asset in the US economy. Williams expects that the rumored investigation and resulting decisions by the US government will have a global impact on the virtual currency industry.



He also expects a short future for MtGox because they’ve broken trust with their customers. “They’re done, they’re toast, they’re Enron – they can’t resurrect themselves,” Williams said.



MtGox’s apparent closure or hiatus also follows the leak of what is alleged to be a “crisis strategy document” from the company, which says that almost 750,000 bitcoins (currently worth more than £200m) are “missing” due to theft which went unnoticed for several years.



“As there is a lot of speculation regarding MtGox and its future, I would like to use this opportunity to reassure everyone that I am still in Japan, and working very hard with the support of different parties to find a solution to our recent issues,” Mt. Gox CEO Mark Karpeles said in a statement on the company’s website.

After the closure, Japanese regulators began examining the legality of bitcoin for the first time.



But the country’s authorities are still declining to take responsibility for bailing out MtGox customers who may have lost bitcoin in the exchange’s troubles.

On Wednesday, a spokesman for the Japanese government told the Wall Street Journal’s Takashi Mochizuki that the government would make “a proper assessment” on the regulation of bitcoin. The spokesman also confirmed that the government was working with the country’s police to collect information on MtGox and was prepared to “take action”.