NEW YORK, Sept. 16 (UPI) -- U.S. markets stumbled at the opening bell Tuesday a day after their worst one-day fall since September 2001.

Investors are keeping an eye on Goldman Sachs Group and Morgan Stanley, the nation's two remaining investment firms, following the loss of Bear Stearns in March and Merrill Lynch and Lehman Brothers Holdings Monday.

Insurance giant American International Group is also not out of the woods, still negotiating for capital to shore up its bottom line.

The Dow Jones industrial average, down 504.48 points Monday, fell 39.24 points in midmorning trading Tuesday, off 0.36 percent at 10,878.27. The Standard & Poor's index was off 9.71 points, or 0.81 percent, to 1,182.99. The Nasdaq composite index was down 12.59, or 0.58 percent, to 2,167.32.

The 10-year U.S. Treasury note rose 29/32 to yield 3.31 percent.

The dollar was mixed. The euro traded at $1.4207 against the dollar, compared with Monday's $1.431, while the dollar traded at 103.905 yen from Monday's 104.88 yen.

In Tokyo, the Nikkei average fell 605.04, down 4.95 percent, to 11,609.72.

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