Japan's vice finance minister Jiro Aichi has called for the international regulation of Bitcoin following the closure of one of the world's largest exchanges of the cryptocurrency, MtGox.
The Japan-based MtGox exchange went offline earlier this week after a "malleability-related theft" cost the firm a reported 744,408 BTC (£230 million).
Aichi said that his ministry was investigating the disappearance of MtGox, together with financial authorities in America.
"It's not just the Ministry of Finance; many other agencies are related," Aichi said. "As for its legal position, a currency (recognised by Japan) would be coins or notes issued by the Bank of Japan.
"At the very least, we can say bitcoin is not a currency."
The troubles faced by MtGox have had significant repercussions on the virtual currency, with its value plunging since users discovered earlier this month that they were unable to make withdrawals from the exchange.
Its failings have received wide-spread criticism and were labelled a "tragic violation of the trust of users" in a joint statement by several key players in the Bitcoin community.
In a statement posted on the MtGox website on Tuesday, CEO Mark Karpeles said: "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."