Stock prices hurtled lower Monday as anxiety overtook investors on the first trading day since Standard & Poor's downgraded American debt.

The Dow Jones industrial average closed down 636 points, losing nearly 5.6 percent of its value.

The Dow fell below 11,000 for the first time since November. The sharp drop extended Wall Street's almost uninterrupted decline since late July, when the Dow was flirting with 13,000.

The stock market plunged at the opening bell, with the Dow down 250 points in minutes. Stocks steadily fell for most of the rest of the morning and early afternoon.

The Dow closed at 10,810. The S&P 500 fell 79 points, or 6.6 percent, to 1,119. The Nasdaq dropped 174 points, or 6.9 percent, to 2,358.

Indiana stocks were part of the carnage. Late in the trading day, Duke Realty Corp. shares were down 13.2 percent. CNO Financial Group was off 12.3 percent, and Brightpoint Inc. had fallen 10.7 percent. HHGregg Inc. suffered a 9.2-percent decline.

ITT Educational Services Inc. shares shed almost 6 percent of  their value. Even Cummins Inc.—which has been enjoying phenomenal growth in China and other world markets—saw the value of its stock fall 7.9 percent.

Among other local companies, shares of Eli Lilly and Co. fell 3.5 percent; WellPoint Inc. dropped 7.6 percent; Simon Property Group  fell 7.7 percent; and The Finish Line sank 5.2 percent.

Investors worried about the slowing U.S. economy, escalating debt problems threatening Europe and the prospect that fear in the markets would reinforce itself, as it did during the financial crisis in the fall of 2008.

They desperately looked for safe places to put their money and settled on U.S. government debt — even though U.S. government debt was the target of an S&P downgrade Friday.

The price of Treasurys rose, and yields, which move in the opposite direction from price, fell. The yield on the 10-year Treasury note fell to 2.33 percent from 2.57 percent Friday.

"This is largely a flight to safety," said Thomas Simons, money market economist with Jefferies & Co. "The bond market is really trading off of what's going on in the stock market."

Gold set a new record, trading for more than $1,700 an ounce.

Stock markets in Asia began Monday's global rout. The main stock index fell almost 4 percent in South Korea and more than 2 percent in Japan. European markets opened later and fell, too, with Germany down 5 percent and France 4.7 percent.

In the U.S., stocks fell even though Moody's, another major credit rating angecy, stood by its top rating of AAA for the United States. It said it could downgrade the U.S. if it cut its deficit, "but it is early to conclude that such measures will not be forthcoming."

Financial markets also did not appear comforted by an afternoon statement by President Barack Obama, who said Washington needs more "common sense and compromise" to tame its debt.

"Markets will rise and fall," he said. "But this is the United States of America. No matter what some agency may say, we've always been and always will be a triple-A country."

S&P, in its downgrade, criticized dysfunction in the American political system. The downgrade wasn't a total surprise but came when investors were already feeling nervous about the U.S. economy and European debt, among other problems.

Last week, the Dow Jones industrial average fell almost 700 points. That was its biggest point loss since October 2008, during the financial crisis. Counting Monday, the Dow has dropped in 10 of the last 12 trading days.