Meanwhile, both fraudsters and promoters of high-risk investment schemes may target bitcoin users, the SEC said. The exchange rate of U.S. dollars to bitcoins has fluctuated dramatically since the first bitcoins were created a few years ago, the agency noted.

The SEC said as the exchange rate of bitcoin is significantly higher today, many early adopters of may have experienced an unexpected increase in wealth, making them attractive targets for criminals as well as promoters of high-risk investment opportunities.

“Fraudsters target any group they think they can convince to trust them. Scam artists may take advantage of bitcoin users' vested interest in the success of Bitcoin to lure these users into bitcoin-related investment schemes,” the SEC said.

The Texas Securities Commissioner recently entered an emergency cease and desist order against a Texas oil and gas exploration company, which claimed it was the first company in the industry to accept bitcoins from investors. The TSC charged the firm with intentionally failing to disclose material facts to investors including “the nature of the risks associated with the use of bitcoin to purchase working interests” in wells, according to the SEC.

The company advertised working interests in wells in West Texas, both at a recent Bitcoin conference and through social media and a web page, according to the emergency order.

In February, the SEC said it suspended trading in the securities of Imogo Mobile Technologies because of questions about the accuracy and adequacy of publicly disseminated information about the company's business, revenue and assets. Shortly before the suspension, the company announced that it was developing a mobile bitcoin platform, which resulted in significant movement in the trading price of the company's securities.

The Financial Industry Regulatory Authority also recently issued an Investor Alert cautioning investors about the risks of buying and using digital currency such as bitcoin.

In addition, the North American Securities Administrators Association included digital currency on its list of the top 10 threats to investors for 2013.

Among the bitcoin investment risks the SEC is concerned with include the virtual currency not being insured and its history of volatility. Because bitcoins are not legal tender, federal, state or foreign governments may restrict their use and exchange. Further, the use of bitcoin may limit a user's recovery in the event of fraud or theft, the SEC said.

Traditional financial institutions including credit unions and banks often are not involved with bitcoin transactions, making it more difficult to follow the flow of money, according to the SEC.

Although the SEC said it regularly obtains information from abroad such as through cross-border agreements, there may be restrictions on how the SEC can use the information and it may take more time to get the information. In some cases, the SEC said it may be unable to obtain information located overseas.

Law enforcement officials may also have difficulty seizing or freezing illicit proceeds held in bitcoins, the SEC said. Bitcoin wallets are encrypted and unlike money held in a credit union, bank or brokerage account, bitcoins may not be held by a third-party custodian, the agency added.

The SEC and other agencies have warned investors interested in bitcoin to be on the lookout for pitches that promise guaranteed high investment returns and those that don't ask for personal net worth or income requirements. Pressure to invest in bitcoin firms right away and unsolicited offers are also red flags, the SEC said.

Federal and state securities laws require investment professionals and their firms who offer and sell investments to be licensed or registered, according to the SECU. Many fraudulent investment schemes involve unlicensed individuals or unregistered firms. The agency advised checking license and registration status by searching the SEC's Investment Adviser Public Disclosure (IAPD) website or FINRA's BrokerCheck website.