Hang Seng index tumbles as commodities prices fall

Hong Kong's Hang Seng index prolonged its losses on Thursday as drop in commodity prices pressed the index into negative territory. Hang Seng index plunged 1.32% or 276.03 points and closed at 20,609.39 with energy sector posting the biggest daily drop. Aluminum Corp. of China lost 1.3% while PetroChina gave up 2%. Cnooc tumbled 3.3% despite reporting better than expected annual net income as oil provider admitted it set a conservative output target for 2012.