BEIJING (AP) — A factory explosion in a port city south of Shanghai on Sunday knocked down nearby residential buildings and sent injured people to hospitals, news reports said. There was no immediate word of possible deaths or how many people were hurt. The explosion at a factory in Ningbo, one of China's busiest ports, struck a neighborhood along the Yong River at about 8:55 a.m., the official Xinhua News Agency and other outlets reported.