Explosion rocks northern Chinese city of Tianjin The explosion was at a port in Tianjing , China. (CNN)A massive explosion shook the northern Chinese city of Tianjin late Wednesday, startling residents and injuring more than 50 people, according to state media. It is not immediately clear whether anyone was killed. The explosion in Tianjin erupted at a container port where flammable material was being stored, reported CCTV, China's state-owned broadcaster. The broadcaster said some firefighters were hurt. The state-run Xinhua news agency reported that a nearby hospital had received more than 50 patients. The initial blast triggered secondary explosions, causing local tremors, Xinhua said. Firefighters were dispatched immediately to the scene, according to the Tianjin Public Security Bureau. The explosion was caused by a shipping container, the bureau said, citing a preliminary analysis. CNN's Steven Jiang contributed to this report.