The bullish dollar exchange traded fund (ETF) has pulled in so much interest recently that trading was briefly halted today so an application for more shares could be filed with the Securities and Exchange Commission (SEC).

After the fund ran out of available shares, trading in PowerShares DB U.S. Dollar Bullish (NYSEArca: UUP) was halted today at 1:23 p.m. ET until a filing with the SEC could be made.

An application for 100 million additional shares was filed and the fund began trading again at 1:51 p.m. ET. As long as no new creation baskets can be issued, UUP runs the risk of trading at a premium to its net asset value (NAV). Investors who want to monitor the intraday indicative value of the fund can visit the ticker page on Yahoo Finance.

UUP is trading at four or five times normal volume today, and until new shares are granted, the fund could continue to trade at a premium. Investors who aren’t comfortable with the premiums should wait until new shares are issued if they plan to buy the fund. Today, UUP is trading at roughly a 1.7% premium.

UUP has been seeing trading volume with moves valued at hundreds of thousands of dollars. Hours before the Federal Reserve announced plans to keep the federal fund target lending rate at current levels, options traders poured into UUP, reports Tennille Tracy for The Wall Street Journal. (ETFs to play the Fed’s move).

UUP tracks the moves of the U.S. dollar against other major currencies. The bulk of the action in the PowerShares fund appears to have been driven by professional investors who emerged to buy options in batches of 10,000 or more, and many of the transactions cost $150,000 and up.

Nguyen Ahn Thu, Darcy Crowe, and Will Conners for The Wall Street Journal report that although the U.S. dollar has lost value, it’s still king on the black market in foreign countries. It’s estimated that as much as 75% of U.S. notes in circulation are held outside the United States, and most of that is in the underground economy.

Residents of poorer countries, such as Venezuela, prize the dollar for its inflation-protection ability against weaker local currencies. (Other reasons foreign countries like a strong U.S. dollar).

For more stories about the U.S. dollar, visit our U.S. dollar category.

Tags: Currency ETFs, U.S. Dollar, UUP