Stocks plunge, wiping out July gains; Market is on track for first monthly loss since January

U.S. stocks are plunging, putting the market on track for its first monthly loss since January.

The Dow Jones industrial average had its worst daily drop since February. At one point it was down more than 300 points.

The slide interrupted a prolonged advance in the market. The Standard & Poor's 500 index closed at its latest record high just one week ago. It's currently 2.7 percent below that level.

Investors responded to several weak earnings reports, escalating geopolitical instability and widespread views that stocks had become too expensive. They are also contemplating the likely end of the Federal Reserve's stimulus program this year.

The Dow was down 273 points, or 1.6 percent, to 16,607 in late trading Thursday. The S&P 500 was down 34, or 1.7 percent, at 1,935.