Each of the major indexes fell at least 2 percent, including the Dow Jones industrial average, which lost more than 300 points.

Stocks opened higher but quickly gave up their gains after the Philadelphia Federal Reserve said its survey of regional manufacturing activity registered a negative 20.9 from a revised reading of negative 1.6 in December. The reading came in well short of what Wall Street had been expecting and underscored the seriousness of the economic concerns that have gripped both Wall Street and Washington in recent weeks.

Credit concerns also dogged Wall Street after rating agency Moody's Investors Service placed bond insurer Ambac Assurance Corp. on review for a possible downgrade. That possibility alarmed Wall Street because it would place all bonds insured by Ambac on review as well. Ratings agencies are concerned that bond insurers would be unable to absorb a spike in claims.

According to preliminary calculations, the Dow, which had been up more than 50 points early in the session, closed down 306.95, or 2.46 percent, at 12,159.21.

The Dow is now off 8.34 percent for the year.

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