* Nasdaq breaches closing record last hit in March 2000
* Indexes: Dow up 0.5 pct, S&P up 0.5 pct, Nasdaq up 0.6 pct (Updates to afternoon trading)
By Caroline Valetkevitch
April 23 (Reuters) - The Nasdaq Composite, the U.S. market index most closely associated with technology stocks, jumped to a 15-year high on Thursday, putting it on track for its first record high close since the technology bubble burst.
The Nasdaq jumped as high as 5,069.17, led by shares of Apple, which has been among the biggest positive influences on the index in recent years. The index's last record close of 5,048.62 was hit on March 10, 2000.
The S&P 500 was also on track for a record closing high. It hit its most recent record close of 2,117.39 on March 2.
Rapid growth in biotechnology companies such as Gilead and social media firms like Facebook, driven by the popularity of mobile computing, have also helped to lift the Nasdaq to its current levels.
Shares of Gilead were up 1 percent at $105.23, while Facebook, which late Wednesday posted quarterly revenue that missed analysts estimates, was down 0.8 percent at $83.99.
Shares of Apple, the most valuable company in the United States, were up 0.9 percent at $129.72, while Google was up 1.5 percent at $547.17.
Strategists say there is still room for the Nasdaq to rise.
Stephen Massocca, chief investment officer at Wedbush Equity Management LLC in San Francisco, said the Nasdaq has a good chance of sustaining its current high levels for some time unless there is a significant change in monetary policy.
But he cautioned that social media stocks within the sector will likely tumble eventually. "I think this is the heart of the story and the speculative fervor. I don't know when it's going to end but I know how it's going to end, badly," Massocca said.
At 2:05 p.m., the Dow Jones industrial average rose 81.56 points, or 0.45 percent, to 18,119.83, the S&P 500 gained 9.95 points, or 0.47 percent, to 2,117.91 and the Nasdaq Composite added 28.17 points, or 0.56 percent, to 5,063.34.
On Thursday, nine of the 10 major S&P sectors were higher, with the energy sector up 1.2 percent following gains in oil prices.
Shares of Dow component Caterpillar gained 1.1 percent to $85.77 following its results.
Advancing issues outnumbered declining ones on the NYSE by 2,145 to 833, for a 2.58-to-1 ratio; on the Nasdaq, 1,739 issues rose and 961 fell, for a 1.81-to-1 ratio favoring advancers. (Additional reporting by Tanya Agrawal, David Randall, Sinead Carew and Rodrigo Campos; Editing by Savio D'Souza and Nick Zieminski)