Benchmark indices have dived into the red on September 20, 2021, dragged by the metal and banking stocks. At the end of the trading session, Sensex plunged by 524.96 points or 0.89 per cent closing at 58,490.93 levels and the Nifty tumbled 188.30 points or 1.07 per cent settling at 17,396.90 levels.