The Sensex opened with a positive gap of 182 points at 10,763, and soon touched a high of 10,787. The index, however, could not go further up as weakness crept into metal and realty stocks.
Selling intensified in the second half of the trading day with forced the index break the 10,000-mark in late trades. The index tumbled to a low of 9,911 - down 876 points from the day's high - a level last seen on July 24, 2006.
The Sensex finally ended with a loss of 669 points at 9,912.