NEW YORK- US stocks tumbled Tuesday after mixed corporate financial results reminded investors of economic troubles and the Federal Reserve took new action to help blocked credit markets.

The Dow Jones Industrial Average plunged 231.77 points (2.50 percent) to close at 9,033.66 and the tech-heavy Nasdaq composite dropped a hefty 73.35 points (4.14 percent) to 1,696.68.

The broad Standard & Poor's 500 index slid 30.35 points (3.08 percent) to 955.05. After a strong rally Monday, the major indices retreated, despite several feeble attempts at a rebound by the Dow. Losses accelerated in a late selloff. "Several companies posted quarterly earnings misses and cautious outlooks that overshadowed signs of improvement in the credit markets," analysts at Briefing.com wrote in a client note.

The interbank lending rate continued to fall in London on Tuesday, slipping below 4.0 percent for the first time since September 19. The Canadian central bank declared the US economy in recession as it announced a second unscheduled interest rate cut this month to stimulate domestic demand.

"The global economy appears to be heading into a mild recession, led by a US economy already in recession," said the Bank of Canada as it gave the reasons for its quarter-point interest rate cut, to 2.25 percent. A surprise lightning visit by Treasury Secretary Henry Paulson, the architect of the massive government bank bailout, to the New York Stock Exchange, where he shook hands with traders and was greeted with applause, did little to soothe nerves.

A wave of US corporate financial results highlighted the challenging economic conditions.

According to Briefing.com, of the 49 companies that issued guidance since late Monday, 45 percent of the guidance was negative, 30 percent was in line with expectations, 21 percent was mixed and only 3.0 percent was positive. Caterpillar, the heavy equipment manufacturer viewed as a bellwether of the US economy, slid 5.06 percent to 38.83 dollars after reporting net profit fell in the third quarter and warning of the "extremely uncertain" outlook because of recent financial market turmoil.

Texas Instruments plunged 6.28 percent to 16.85 after posting a 26 percent fall in quarterly net profit.

Chemicals giant DuPont nosedived 7.99 percent to 33.28 after reporting a steep profit drop and lowering its guidance, citing expected declining demand in the US and Europe.

With oil prices falling, ExxonMobil, the Dow's largest component, dropped 4.65 percent to 71.50.

Pfizer closed flat off earlier gains, at 17.34. The pharmaceutical giant reported third-quarter net profit tripled from a year ago and raised earnings guidance for 2008.

Ailing automaker Ford was in focus after billionaire US investor Kirk Kerkorian's announced, via his holding company Tracinda, that he was putting the brakes on his stake in Ford and may divest his entire investment. Shares in Ford skidded 6.87 percent to 2.17 dollars.

UAL, the parent of United Airlines, soared 8.92 percent to 13.80 on a heavy third-quarter loss that was not as bad as market expectations.

Bonds surged. The yield on the 10-year US Treasury bond dropped to 3.703 percent from 3.886 percent Monday, and that on the 30-year bond fell to 4.194 percent from 4.284 percent. Bond yields and prices move in opposite directions.