A survey on hiring did little to ease uncertainty about the health of the economy.
The Dow teetered between slight gains and losses as the sell-off eased by late afternoon. But the upswing ultimately didn't hold.
The Dow Jones industrial average dipped 5.01 points, 0.03 percent, to 15,440.23.
The Standard & Poor's 500 index fell 3.56 points, or 0.2 percent, to close at 1,751.64.
The Nasdaq composite dropped 19.97 points, or 0.5 percent, to 4,011.55.
For the week so far:
The Dow is down 258.62 points, or 1.7 percent.
The S&P 500 is down 30.95 points, or 1.7 percent.
The Nasdaq is down 92.33 points, or 2.3 percent.
For the year so far:
The Dow is down 1,136.43 points, or 6.9 percent.
The S&P 500 is down 96.72 points, or 5.2 percent.
The Nasdaq is down 165.04 points, or 4.0 percent.