A powerful explosion ignited by a broken gas pipeline on Wednesday killed at least 12 people, injured about 300 and flattened hundreds of buildings in eastern China in the latest in a series of troubling industrial accidents. The blast occurred at 10:15 a.m. local time Wednesday at a plastics factory in Nanjing, the capital of Jiangsu province. According to state media, the explosion occurred when workers at the factory dug into a nearby polyethylene pipeline. The blast was so strong, many residents mistook it for an earthquake. Almost all structures within 100 yards of the blast in the residential area of Qixia district collapsed, many of them old single-story homes marked for demolition. Several two- and three-story buildings also collapsed.The accident was the latest to raise concerns about industrial safety in China. An explosion at the northwestern port of Dalian this month caused one of the largest oil spills ever in the country. An acid leak at a gold and copper mine in Fujian province poisoned a nearby river, killing 2,000 tons of fish. "These accidents are not unpredictable but, rather, are the inevitable consequence of inadequate transparency and weak enforcement" of safety standards, said Alex Wang, senior attorney in the Beijing office of the Natural Resources Defense Council. The blast Wednesday filled Nanjing with black smoke. Witnesses near the accident said streets were covered with broken glass and blood.