NEW YORK (TheStreet) -- Stocks sold off at the start of the new quarter as disappointing jobless claims data left Wall Street bracing for Friday's unemployment report. After locking in 15% gains for the third quarter, the Dow Jones Industrial Average started off the new three-month period by taking a 204.89-point plunge, dropping 2.1%, to 9507.39, while the S&P 500 slid 27.4 points, or 2.6%, to 1029.68. The Nasdaq Composite edged down 64.94 points, or 3.1%, to 2057.48.
Losses were broadbased with financials, commodities, technology and home stocks hard hit. The Philadelphia Stock Exchange Gold and Silver Index, the Philadelphia Semiconductor Index, and the KBW Bank Index all sank more than 4%.
Stocks fell early after the Department of Labor said there were 551,000 new jobless claims last week, up from an upwardly revised 534,000 the week prior and topping expectations for 535,000.
Those data, paired with a worse than expected report on private sector job losses earlier in the week, have traders cautious ahead of the most-anticipated data of the week, Friday's unemployment report, says Doug Roberts, chief investment strategist at ChannelCapitalResearch.com.
"You've seen chinks in the armor, so people are hesitant -- especially with it coming on a Friday," says Roberts. "There's uncertainty, and until there's some sort of resolution, people are going to be nervous."
Adding pressure to the market, Goldman Sachs changed its forecast for September nonfarm payrolls from a loss of 200,000 to a loss of 250,000, wrote James DePorre, founder and CEO of Shark Asset Management, on RealMoney.com.
In other data Thursday, Institute for Supply Management's manufacturing index edged down 0.3 points to 53.6, vs. expectations for a rise to 54. The Chicago PMI spurred selling earlier in the week, when it indicated a contraction in manufacturing.
"Tentative signs in housing, automobile, Chicago PMI and several other economic indicators continue to remind us that the month of September was weaker than generally expected," writes Seabreeze Partners' Doug Kass. He later adds that, "at the risk of being the boy who cried wolf, I believe that market participants have a false sense of security in rising equity share prices."
"Plenty of stocks were pumped up by mark-up buying. The pump-up and subsequent support underneath is now gone," writes Jim Cramer on RealMoney.com."We know that jobless claims aren't improving. That's a real negative, especially for retail and banks. But, and this is a big but, we are not seeing the right stocks go up if we are signaling another dip down."
Not all of the recent data have been negative. Among the day's surprises, construction spending unexpectedly increased by 0.8% in August, and pending home sales rose by 6.4% vs. expectations for a much smaller, 1% gain.
At the same time, the Department of Commerce said personal income increased 0.2% in August, in line with the prior month's increase, and spending ticked up 1.3%, respectively, vs. 0.3% in July. Both readings were slightly better than expected.
In other news Thursday, Federal Reserve Chairman Ben Bernanke testified before the House Financial Services Committee on regulatory reform. Bernanke told members of Congress that a council of regulators should monitor systemic risk, while all systemically important financial firms should be subject to a consolidated regulator.