The Sensex at the Bombay Stock Exchange was trading 177 points in the negative zone at 16,537 when reports last came in. The 30-share index which had lost 108 points in the previous session on Monday fell by 97 points in opening trade on Tuesday.In a similar fashion, the wide-based National Stock Exchange Nifty index was down by 58 points at 4,959.In the Asian region, Hong Kong's Hang Seng Index fell by 1.02 per cent, while Japan's Nikkei Index shed 1.40 per cent in morning trade on Tuesday.