NEW YORK (AP) - Biotech and Internet stocks tumbled again Thursday, and the broader market followed.
After a two-day respite, investors again started dumping shares of cutting-edge drug companies and other industries that have soared over the past year. Biotechnology stocks have turned volatile in recent weeks as regulators scrutinize the cost of their drugs and investors worry their earnings won't justify lofty stock prices.
On Thursday, the Nasdaq composite, which is weighted heavily toward tech and biotech companies, had its worst day since November 2011.
The rout started slowly and picked up speed throughout the day. By the close, the tech-heavy Nasdaq composite index had its worst day since November 2011. Few companies escaped the sell-off.
Of the Nasdaq's 100 largest stocks, only one, C.H. Robinson Worldwide, a freight company, ended higher.
The Nasdaq ended the day down 129.79 points, or 3.1 percent, to 4,054.11. It is now down 7 percent from its recent high reached March 5.
Other major index also fell, but not as much.
The Standard & Poor's 500 index dropped 39.10 points, or 2.1 percent, to close at 1,838.08. The Dow Jones industrial average lost 266.96 points, or 1.6 percent, to 16,170.22.
Biogen Idec, Gilead Sciences and other biotech companies plunged. Facebook and Twitter, other recent investor favorites, also dropped.
The sudden downfall of these former high-flyers comes as investors shift from riskier investments to safer areas like utilities, health care and consumer staples. The sell-off in these former darlings, whose stock prices appealed to investors because their rise seemed unstoppable, has weighed on the overall market, especially the Nasdaq.