On Tuesday, federal agents froze an account belonging to a popular exchange for the Internet currency called bitcoins.

The Department of Homeland Security obtained a warrant to seize the account, administered by payment provider Dwolla. Earlier this week, the department alleged that Mutum Sigillum LLC, a subsidiary of Mt. Gox, was not registered with FinCen, the Treasury Department’s Financial Crimes Enforcement Network. In the warrant, the government said it had probable cause to believe that the account was used to “conduct transactions as part of an unlicensed money service business,” the Wall Street Journal noted.

Mt. Gox, based in Tokyo, was established in 2010. As of this year, it was cited as the world’s largest bitcoin exchange, handling 63% of all worldwide bitcoin transactions. In an online statement, Mt. Gox said it had not received a copy of the warrant and did not know why the account had been seized.

A spokesman for Dwolla said that the company did not consider itself involved in the matter and had informed users of the account about the situation.

Earlier this month, Cameron and Tyler Winklevoss, the twins who sued Mark Zuckerberg over their role in the founding of Facebook (NASDAQ:FB), announced that they had purchased $11 million worth of bitcoins.