Hundreds of people have been evacuated from their homes in north-eastern China after a leak of toxic chemicals into a river. The residents were put onto trains as an 80 kilometre-long slick of water contaminated by benzene and other substances passed by on the Songhua river.The water supply to affected areas has been cut intermittently and bottled drinking water has been brought in by truck. About 1,000 soldiers and paramilitary police have been deployed at several water plants to install filters that can more effectively absorb the pollutants. The contamination followed an explosion at a petrochemical plant Jilin. The main population centre under threat is Harbin, a city of nine million people. But authorities in Russia have also expressed concern. Experts have been monitoring the water of the Songhua river which enters Russia several hundred kilometres downstream from Harbin. China has rejected accusations that it waited too long before informing Russia of the incident.