NEW YORK (CNNMoney.com) -- Stocks undulated Tuesday afternoon, turning higher and lower minutes after the Fed left interest rates unchanged for the first time in more than two years amid worries about a slowing economy .

The Dow Jones industrial average (Charts), the broader Standard & Poor's 500 (Charts) index and the tech-fueled Nasdaq composite (Charts) all declined as of 2:30 p.m ET, roughly 15 minutes after the announcement.

Stocks had briefly rallied, before switching directions as investors digested the statement more closely.

As expected, the central bank voted to keep the fed funds rate, a key overnight bank lending rate, at 5.25 percent, unchanged from the last meeting, after raising it 17 times in a row.

In the closely-watched statement, the Fed said that the upward pressure on inflation could moderate in the months ahead, meaning that the bank won't necessarily have to restart its rate-hiking campaign.

However, the Fed also said that "economic growth has moderated," a more decisive take on the economic slowdown than perhaps what investors were looking for. That sent stocks lower.

Treasury prices were little changed on the news, with the yield on the benchmark 10-year note at 4.92 percent, little changed from late Monday. Prices and yields move in opposite directions.