NEW YORK - Two companies withdrew their plans to raise money through initial public offerings last week, adding to a growing list of pulled IPO deals, as volatile markets make investors wary.

Amid the turmoil, real estate investment trust Welsh Property Trust Inc. and Nobao Renewable Energy Holdings Ltd., which makes pumps used to heat and cool commercial buildings, had been expected to start trading Friday.

As if to underscore the continuing market churns, the Dow Jones industrial average dropped 323 points Friday, its third-worst slide of the year. The index closed below 10,000 for the second time in two weeks.

The IPO market has cooled as investors perceive the deals as too risky.

Analysts say Welsh Property Trust competes with other well-established REITs offering higher yields with less risk, while Nobao has a low-tech business and no established history of successful manufacturing.

Meanwhile, companies drawing interest from investors, such as the Chicago Board Options Exchange Inc., financial-services company Green Dot Corp., and video game rental service GameFly Inc., are waiting for a better time to come to market.

About a third of the companies planning IPOs last month postponed or withdrew their deals. Those that made it to market offered deep discounts to entice investors as stock markets traded wildly.

The volatility that has plagued the broader market continued Friday as stocks fell sharply after a government report that showed hiring remains weak.

Investors are also concerned about the effect that Europe's economic problems could have on the United States. Traders have taken a dimmer view of Europe's debt problems and deep government spending cuts, which have pressured the euro, the currency used by 16 European nations.

The market also has been vulnerable to swings because of worries about the economic fallout from the Gulf of Mexico oil spill.

For the week, the Dow lost 2 percent, its third straight weekly drop. The broader S&P 500 index fell 2.3 percent, and the Nasdaq dropped 1.7 percent.

Investors moved money into safe investments including Treasuries on Friday because of the weak employment report and a faltering euro.

The yield on the 10-year Treasury note, which moves opposite its price, fell to 3.21 percent from 3.37 percent late Thursday. The yield on the 10-year note is often used as a benchmark for consumer loans and mortgages.

Analysts say there is little in the way of economic news that could shake the market from its funk.

"It's hard to see over the next month what will make stocks rally," said Paul Zemsky, head of asset allocation at ING Investment Management in New York. It might not be until next month's employment report that investors get the kind of positive news that could propel stocks higher, he said.

All the uncertainty has kept many companies away from the IPO market. Only two companies are scheduled to debut this coming week: video ringtone service Vringo Inc. and corn-based alcohol producer China New Borun Corp.