U.S. regulators temporarily suspended trading in an obscure digital currency company because of concerns that its stock is being manipulated after the shares surged more than 17,000 percent in less than three months, making paper billionaires out of top executives.

In a Tuesday order halting buying and selling of The Crypto Co., the Securities and Exchange Commission said it was worried that investors aren’t getting accurate disclosures or enough information about the company. Questions have also arisen about “potentially manipulative transactions” involving the California-based company’s shares, the SEC said.

Crypto appears to be a beneficiary of the digital-currency fever that has gripped markets in 2017. Despite losing more than $2.7 million this year and posting just a few hundred thousand dollars of revenue, the company’s market capitalization exceeds $11 billion. Its lofty valuation has made a billionaire out of President James Gilbert, who held a stake worth nearly $4.2 billion based on Monday’s closing price.

Crypto trades over-the-counter, a market that typically has less stringent oversight than regulated exchanges. Its share jump has attracted the attention of market operator OTC Markets Group, which added a skull-and-crossbones icon next to the company’s stock symbol this month to urge investors to be extra cautious before buying the shares.

The company invests in digital assets and is developing source code for managing them, according to regulatory filings. At the end of September, it held cryptocurrencies worth $900,110, filings show. Bitcoin, the biggest digital currency, was trading for about $4,171 at the time, but has since surged to more than $18,220.

The SEC said its concerns about Crypto include the compensation paid for the promotion of the company and statements made in regulatory filings about plans for insiders to sell their shares. The company didn’t immediately respond to a request for comment. The temporary suspension will last through Jan. 3, according to the SEC order.

Wall Street’s main regulator has been cracking down on offerings tied to cryptocurrencies because of concerns that some companies aren’t complying with securities rules and that investors could get fleeced.

This month, the SEC froze the assets of an initial coin offering that promised a 13-fold profit in less than a month. The agency alleged that the offering violated federal securities laws because it was not registered with the government.

Crypto disclosed last week that it was selling shares privately for $7, a steep discount to the $223 that investors were paying for its stock in public markets at the time. Chief Executive Officer Michael Poutre said the $7 price had been communicated to potential buyers weeks ago – before the stock’s dramatic surge. The stock peaked at $642 on Dec. 11 before closing at $575 Monday.

Crypto also disclosed last week that it plans to split its shares 10-for-1, citing the recent jump in the stock price and the recent “rise of the entire digital-currency market.” The company is the product of a reverse merger with a sports bra company.