NEW YORK (CNN/Money) - U.S. stock markets sank deeply into negative territory Wednesday afternoon after the Federal Reserve left interest rates unchanged but altered the language of the statement it released at the end of its policy meeting.

Instead of indicating that interest rates will stay low for a "considerable period of time," the central bank said it could be "patient in removing its policy accommodation" -- a choice of words that appeared to leave the markets perplexed and caused a sell-off on Wall Street.

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At around 2:45 p.m. ET, about half an hour after the Fed announcement was released, the Dow Jones industrial average (down 100.96 to 10508.96, Charts), the Standard & Poor's 500 (down 11.03 to 1133.02, Charts) index and the Nasdaq composite (down 22.55 to 2093.49, Charts) all showed losses of more than 1 percent after trading higher all day prior to the Fed news.

Bonds sold off as well. The 10-year Treasury note shed almost a full point in price, its yield jumping to 4.19 percent from 4.07 percent late Tuesday.