An NSE official said the falls appeared to have come from a single broker and the exchange was looking into the matter.
The falls were within the exchange's limits, he added.
Tata Motors shares fell 5.5% after six separate block deals comprising a total 2.07 million shares took place at an average price of Rs.275.
The sales sent Tata's shares as low as Rs.268, before recovering to close the day at Rs.293, down 1.7% on the NSE.
Ultratech shares fell 3.4% after one block deal comprising 41,863 shares took place at an average price of Rs.1,854.
Shares fell to Rs.1,712 but closed the day at Rs.1,870, down 1.7% on the NSE.