NEW YORK (AP) -- Stocks fell Monday as worries flared anew about the European debt crisis.
The Dow Jones industrial average was down 20 points at 13,255 at shortly after noon EDT. The Standard & Poor's 500 was off four points at 1,415. And the Nasdaq composite index was down almost 10 points at 3,067.
In a report issued Monday, the German central bank questioned the wisdom of having the European Central Bank buy bonds to help the struggling European economies. It stressed that such purchases could carry "substantial risks."
Earlier this month, stocks rallied after ECB President Mario Draghi said the bank might buy government bonds of struggling European countries to help lower their borrowing costs.
German Chancellor Angela Merkel, who has resisted easing pressure on struggling countries, also heartened investors with comments last week that officials would do everything possible to save the euro.
In the U.S., Lowe's, the world's No. 2 home improvement store, missed earnings expectations Monday. Revenue at stores open at least a year dipped 0.4 percent, and the company cut its outlook for the year. The stock fell 5 percent.
Stocks have been inching up for six weeks. On Friday, both the Dow and the S&P closed just below four-year highs.
Other stocks moving sharply early Monday included health insurer Aetna, which announced it would buy Coventry Health Care for $5.7 billion as the insurance industry realigns itself to better navigate the health care overhaul.
Aetna rose $1.12, or 3 percent, to $39.16. Coventry climbed $6.39, or 18 percent, to $41.33.
The deal follows the $4.46 billion buyout last month of another insurer by WellPoint Inc., and last year's acquisition worth nearly $4 billion by Cigna of HealthSpring as it grabbed for a share of Medicare revenue.
Best Buy slid 7 percent after rejecting an offer from its founder and largest shareholder to take the electronics retailer private. The company named Hubert Joly, the former head of global hospitality company Carlson and a turnaround expert, as CEO Monday.
Facebook fell 17 cents, or nearly 1 percent, to $18.88, continuing a steep slide from its offering price of $38 when the stock debuted on the public markets in May.
All 10 industry groups in the S&P 500 fell, led by telecommunications and consumer discretionary stocks. Those were down more than 0.5 percent each.
In Europe, stocks were also falling. Greek and Spanish stocks were each down about 2 percent.
Investors are keeping an eye this week on a series of meetings among European leaders to discuss the debt crisis. On Monday, the Greek foreign minister met with his German counterpart in Berlin to discuss Greek spending cuts necessary for the country to continue receiving bailout money to avoid bankruptcy.