Explosion in a 15-meter-high sewage tank at a factory in east China's Zhejiang Province on Tuesday led to a collapse that left four people dead, 16 injured and several others trapped. Over 110 firefighters were dispatched to the site for rescue. As of 9:30 p.m. on Tuesday, 20 people had been rescued. The injured have been sent to the hospital, while rescue work is still underway.