Extending its losses, the Sensex at the Bombay Stock Exchange was down 183 points, or 0.9 percent, at 19,401, in afternoon trade, a short while ago. Earlier, in the morning, the Sensex had opened 107 points, or 0.6 per cent in the negative zone, at 19,477, on continued selling by investors, ahead of the expiry of the monthly derivatives contracts, and in line with a weak trend on the other Asian bourses.Stock markets in Japan, China, Hong Kong, Indonesia, Singapore, South Korea and Taiwan were down by between 0.1 percent and 1.2 percent, today. Over in the US, the Dow Jones Industrial Average had lost 0.2 per cent, overnight.