NEW YORK (CNNMoney.com) -- Stocks gained some ground near midday Tuesday, finding momentum after a sleepy morning, thanks to falling oil prices and a rally in the tech and commodity sectors.

The Dow Jones industrial average (up 16.25 to 11,480.40, Charts) and the broader Standard & Poor's 500 (up 2.97 to 1,313.98, Charts) index both added around 0.2 percent roughly 2-1/2 hours into the session.

The Nasdaq composite (up 12.43 to 2,205.59, Charts) added 0.5 percent.

Stocks swayed in a tight range through the morning as investors welcomed the fall in oil prices, but showed some reluctance to bid stock prices higher after last week's big advance. A rise in Treasury bond yields had added to the early weakness as well.

But the market staged a move to the upside heading into the lunch hour, as traders filed back in after the long holiday weekend. U.S. financial markets were closed Monday for the Labor Day holiday.

Stocks gained in August and on Friday, the first day of September, as investors welcomed lower oil prices and reports that seemed to suggest the economy was holding up, but not growing so aggressively as to put upward pressure on prices.

Such bets are likely to keep supporting stocks in the short term, said Art Hogan, chief market analyst at Jefferies & Co, as Wall Street attendance heats up this week after a typically slow end-of-summer.

"As people try to get back into the game, there's excitement about the prospect of an economy that shows strength and sustainable growth, but that isn't overly inflationary," he said.

In order for the market to build on recent gains, investors will be looking for more good news on the corporate front, as well as additional solid economic data and lower energy prices, he said.

U.S. light crude oil for October delivery sank 79 cents to $68.40 a barrel on the New York Mercantile Exchange. Prices dipped after the discovery of a deep-water well in the Gulf of Mexico raised hopes about an increased source of domestic oil production.

Chevron (up $2.18 to $67.01, Charts) and Devon Energy (up $7.18 to $71.33, Charts), two of the three companies that discovered the well, rallied. Others in the energy sector gained too.

Treasury prices slid, as traders took profits off the recent advance. The decline raised the yield on the 10-year note to about 4.77 percent from 4.73 percent Friday. Bond prices and yields move in opposite directions.

In currency trading, the dollar rose against the euro and was little changed against the yen.

COMEX gold for December delivery rose $12.40 to $645 an ounce.

In global trade, major Asian markets mostly ended higher; European markets fell at midday.

Viacom (down $1.52 to $35.45, Charts) shares slipped on news that Tom Freston, its president and CEO, has resigned. The struggling media company will replace him with Philippe Dauman, a member of the Viacom board of directors. (Full Story).

Veritas DGC (up $7.22 to $69.40, Charts) jumped 12 percent on news that it has accepted a $3.1 billion buyout offer from Compagnie Generale de Geophysique, a French provider of gear and services to the oil and gas industries.

The rally in gold sent shares of gold stocks higher, with the Amex Gold Bugs (up $12.68 to $365.90, Charts) index adding more than 2 percent.

Among other stock movers, Bristol-Myers Squibb (down $0.23 to $22.72, Charts) and partner Sanofi-Aventis (down $0.66 to $44.71, Charts) both slipped after warning late last week that earnings will be hurt this year by generic sales of their blood thinner Plavix.

A judge ruled last week that Canadian generic company Apotex must halt sales but did not say the company must recall already distributed drugs.

Market breadth was positive. On the New York Stock Exchange, winners beat losers three to two on volume of 570 million shares. On the Nasdaq, advancers topped decliners by nine to five on volume of 810 million shares.

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