In the ongoing COVID-19 crisis, the Sensex on Monday tumbled about 470 points, dragged by losses mainly in index heavyweights HDFC twins, RIL and ICICI Bank as investors weighed the possibility of a lockdown extension amid mounting Covid-19 cases in the country. After hitting a low of 30,474.15 during the day, the 30-share BSE barometer ended 469.60 points or 1.51 percent lower at 30,690.02.