AIG, Wal-Mart Knock Stock Market Lower

Updated from 4:06 p.m. EDT

Stocks in the U.S. slid Thursday following two days of gains in New York, as shares in AIG (AIG Quote) and Wal-Mart (WMT Quote) were weak throughout the session.

The Dow Jones Industrial Average sank 224.64 points, or 1.9%, to 11,431.43, and the S&P 500 lost 23.13 points, or 1.8%, to 1266.06. The Nasdaq was off 22.64 points, or almost 1%, at 2355.73.

While the market was in the red all day, selling picked up late after Moody's said it has placed the long-term ratings for American Express (AXP Quote) on review for a possible downgrade. Shares of American Express shed 4.2%.

One of the primary factors weighing on equities from the outset was insurer AIG, who lost $5.36 billion in the second quarter as the continuation of the weak U.S. housing market and disruption in the credit markets dragged down its results. The stock plunged 18%.

Retailers also reported their monthly sales results, and many of them fell short of estimates, including Wal-Mart, the largest chain-store operator in the world.

Wal-Mart's U.S. same-store sales, excluding fuel, were up 3% last month, but that missed expectations. Additionally, the company offered cautious comments for spending in August, and its stock fell more than 6%.

Competitor Target (TGT Quote) had a steeper-than-expected decline of 1.2% in its July comps, while Kohl's (KSS Quote) disappointed analysts with a 10.4% pullback.

However, Costco (COST Quote) exceeded forecasts with a 10% increase in same-store sales, and BJ's Wholesale (BJ Quote) had strong numbers.