In afternoon trade, the Sensex at the Bombay Stock Exchange was trading 273 points in the negative territory at 16,180 when reports last came in. The 30-share index, which had lost 244 points in the previous session on Friday, plummeted further by 262 points, to around 16,192 in opening trade today amid sustained selling pressure influenced by a weakening trend in Asian markets on worries over the euro zone debt crisis.In a similar fashion, the wide-based National Stock Exchange Nifty index was trading 81 points in the red at 4,862 points.