Only 76 million shares of indexed companies were traded over the day, with a combined worth of Rs4.46 billion.
The index marked a day's high of 40,373 before rapidly losing ground, reaching a low of 30,067 almost an hour before market close.
Of the 316 symbols traded, only 32 advanced while 265 registered losses. Nineteen closed unchanged. Commercial Banks were the focus of traders' attention, with power generation, cement, chemical and technology stocks following.