At least 75 people have been killed and 185 injured in a factory explosion in China, authorities said Monday.There were around 264 people at the site in east China's Kunshan city in Jiangsu province when an explosion hit a workshop owned by the Taiwanese-invested Kunshan Zhongrong Metal company Saturday, Xinhua reported.Kunshan Zhongrong's two senior executives have been placed under police custody, sources said.Officials have said the explosion was a work-safety accident, and the blast was probably caused by flames igniting dust inside the workshop.