The US Marshals Service is in charge of auctioning off almost 30,000 bitcoins that the federal government seized from Silk Road servers last year, and it had planned to do so in an anonymous auction this month. But that anonymity was compromised on Wednesday when the US Marshals Service accidentally revealed the names of several potential bidders by sending around an auction FAQ to a group of e-mail addresses that it placed in the CC field rather than in the BCC field.

As CoinDesk first reported, Lynzey Donahue, a US Marshals spokeswoman, said that “The message was not intended for any particular group of people, but for anyone who had e-mailed a question to the general mailbox to ask about the auction. Only recipient e-mail addresses were disclosed.” Donahue added that “The USMS apologizes for this mistake which was in no way intentional.” Although not everyone on the list is a potential bidder in the upcoming auction, TechCrunch shows the subject of the e-mail as “Bitcoin Auction Frequently Asked Questions,” so it's safe to assume that at least some of the names on the list are likely interested in placing a bid.

The tens of thousands of bitcoins up for auction are currently worth around $18 million. The US Marshals hopes to auction off the bitcoins in several blocks.

CoinDesk lists 17 people whose names were on the e-mail, including executives at some major finance companies, as well as private investors.

Bidder registration began on June 16 and will close on June 23. Prospective bidders are required to submit a government-issued ID and $200,000 to enter the bidding. Winners must pay in cash and may not pay in installments. Bidders are also required to certify that they are not “acting on behalf of or in concert with the Silk Road and/or Ross William Ulbricht.”