Wall Street dropped in volatile trading today as investors pulled away from stocks amid worries about the credit and housing markets and disappointing corporate earnings.

The market remained uneasy although several companies including drug maker Merck & Co. and toymaker Hasbro Inc. reported decent third-quarter results. Investors were still mindful of the downbeat profit outlooks from some blue chip companies last week and Standard & Poor’s downgrade of another series of mortgage-backed securities; those developments sent stocks plunging Friday, taking the Dow Jones industrials down 366 points.

Over the weekend, the world’s economic leaders not only said that calming the turbulent global financial markets will require vigilance, but they also warned of inflation risks — which puts central banks like the U.S. Federal Reserve in a tight spot. The Fed lowered interest rates on September 18 to make borrowing cheaper amid a growing credit market crisis, and Wall Street hopes policy makers reduce rates again when they meet next week.

Fed Governor Randall Kroszner at a speech in Washington reaffirmed that the central bank will “act as needed” to calm the financial markets, according to Dow Jones Newswires. He also said problems with structured credit products — which dampened the profits at several banks in the third quarter — are recovering, but gradually.

Though the Fed is willing to help boost liquidity, concerns about problems in the financial industry are running high — concerns that make the record highs reached last week by the Dow and the Standard & Poor’s 500 index appear unreasonable.

“It may take a little time here, a week or two, of trying to heal,” chief market strategist at Weeden & Co, Steven Goldman, said. “As we enter the last two months of year, we have a better opportunity to get back to those levels by year end.”

In late morning trading, the Dow was off 89.99, or 0.43%, at 13,432.03, after falling more than 100 points earlier in the session.

The S&P 500 index fell 7.92, or 0.53%, at 1,492.71.