The Nasdaq composite index tumbled yesterday, sustaining its second-worst point drop in history, as biotechnology stocks plunged and investors continued taking profits from the Nasdaq's strong run this year. The Dow Jones industrials followed, giving up early gains and also closing sharply lower.

The technology-dominated Nasdaq fell 200.70, to 4,706.63. With Monday's 141-point loss, the Nasdaq has shed 6.8 per cent in two sessions.

The Dow fell 135.89, to close at 9,811.24. Selling pressure accelerated in the final half-hour of trading. Broad market indexes were lower.

The Standard and Poor's 500 fell 24.47 to 1,359.15.