The Sensex at the Bombay Stock Exchange continuing its downward trend, plunged by 150 points to 17,370 a short while ago. The 30-share barometer had earlier shed 123 points to 17,398 in late morning deals. In the opening trade the BSE benchmark index fell by almost 108 points to 17,413 as funds and retail investors indulged in selling amid a weakening trend on Asian Bourses.Similarly, the Nifty at the National Stock Exchange, declined by 45 points, to 5,271.