The market turned sharply lower in late afternoon when Standard & Poor's again reduced its ratings on residential mortgage-backed securities. The latest reduction, on more than 1,400 types of securities, added to investors' unease about credit quality.

In addition, mixed results from Dow components Caterpillar Inc., Honeywell Inc., and 3M Co. gave investors little incentive to take chances on the market. And oil prices added to investors' list of concerns after briefly moving above the psychological barrier of $90 per barrel for the first time.

In one bright spot, Google Inc. reported stronger-than-expected profits, drawing a number of analyst upgrades.

"I was not surprised there was some correction, given our expectation that earnings growth was going to fall short of expectations," said Alan Gayle, senior investment strategist, director of asset allocation for Trusco Capital Management.

"I think stock analysts were slow to incorporate the impact of the subprime crisis on third-quarter earnings," he added.

According to preliminary calculations, the Dow fell 366.94, or 2.64 percent, to 13,522.02. The Dow was down for the fifth straight session.

Broader stock indicators also fell. The Standard & Poor's 500 index fell 39.45, or 2.56 percent, to 1,500.63, and the Nasdaq composite index dropped 74.15, or 2.65 percent, to 2,725.16. The Nasdaq fell below the noteworthy technical level of 2,750, adding to selling pressure.

Today's pullback pales in comparison to what traders on the floor of the New York Stock Exchange had to contend with 20 years ago. On Oct. 19, 1987 — Black Monday — the Dow plunged 23 percent amid concerns about interest rates and slowing economic growth. A decline of similar proportion given the market's current levels would mean a drop of some 3,000 points.

A decline today in the NYSE composite index proved steep enough, however, to trigger trading curbs, which puts restrictions on certain types of sell orders. These protections were set up in part in response to Black Monday.

Bonds prices rose again today, extending a rally to an unusual five sessions. The yield on the benchmark 10-year Treasury note, which moves inversely to the price, fell to 4.40 percent from 4.50 percent late yesterday. The dollar was mixed against other major currencies, while gold prices fell.

After touching $90.07 overnight, light, sweet crude fell 87 cents to settle at $88.60 on the New York Mercantile Exchange. Prices have spiked due amid forces such as a weak dollar and thin supplies at a key Midwest oil terminal.

"Investors are starting to get concerned about both the pace of the U.S. economy and the pace of earnings growth," said Art Hogan, chief market strategist at Jefferies & Co.

"We've got a multitude of earnings that are less than optimal in spaces outside the financials," he said.

Hogan noted that for much of the week investors focused on results from banks, which saw profits drop on souring mortgage loans and tight credit markets. But seeing weakness yesterday in industrial company earnings reports increased their nervousness.

Caterpillar, one of the world's largest construction equipment makers, fell $4.09, or 5.3 percent, to $73.57 after its third-quarter earnings rose 21 percent but fell short of Wall Street's expectations. In addition, the company lowered its full-year forecast.

Honeywell International Inc., the diversified manufacturer, turned in a 14 percent increase in its third-quarter earnings. The company raised its forecast for full-year earnings to the high end of its previously targeted range. An analyst, however, described profit margins at the company's transportation and automation and controls segments as disappointing. The stock declined $2.37, or 3.9 percent, to $58.32.

3M, the maker of Scotch tape and Post-It Notes, said quarterly profit jumped 7 percent on strong growth across all regions, but sales missed expectations. The company raised its profit outlook for the full year. But the company announced plans to cut prices on its profitable films for LCD television screens. The stock fell $8.11, or 8.6 percent, to $86.62.

Wachovia Corp. fell $1.74, or 3.6 percent, to $46.40 after reporting third-quarter profits fell 10 percent due to write-downs related to difficult credit market conditions. The nation's fourth largest bank signaled increasing credit troubles ahead and said there would be staff cuts.

Google rose $5.09 to $644.71 after the search engine leader said advertising spending lifted third-quarter profit by 46 percent.

Declining issues outnumbered advancers by more than 5 to 1 on the New York Stock Exchange, where volume came to 1.79 billion shares compared with 1.27 billion shares traded yesterday.

The Russell 2000 index of smaller companies fell 26.24, or 3.18 percent, to 798.79.