New Delhi, Aug. 26 -- The abrupt swing in the Nifty that marked the debut of the closing auction session (CAS) on 3 August returned on Wednesday, this time in the opposite direction.

In just 30 seconds after CAS opened at 3:20 pm, the bellwether index slumped 271.4 points or 1.11% to 24005.5, from its reference rate of 24276.9 released at 3:15 pm. Though the index recovered to close at 24207.75, just 0.28% below the reference rate by 3:30 pm, the abrupt slump caught market participants off-guard. At close, the Nifty settled 0.52% below Tuesday's close, while the BSE Sensex closed 0.24% lower.

The slump was attributed to a bid placed 3% below the reference rate for Bharti Airtel, the stock that saw the highest volumes during CAS. While t...