More than 1,000 people fled their homes and businesses and four factory workers were sent to the hospital after a chemical leak at a shoe factory in eastern China over the weekend, according to a statement posted on the local government Web site Monday. Twenty tons of the chemical styrene leaked from containers Sunday at the Hongchang Shoe Materials Co. Ltd. in Wenzhou city in China's eastern Zhejiang province, the report on the Wenzhou government site said. The four workers had nose, eye and throat irritation after coming in contact with the carcinogenic liquid chemical used to make rubber and plastic, the report said. Calls to the Wenzhou city government rang unanswered early Monday. The cause of the leak is under investigation. The danger had passed by late Sunday and all residents returned to their homes, the report said. Workplace accidents are common in China, where thousands die every year in part because of lax enforcement of safety rules and poor worker training. Less than a week ago, four people died and 108 were injured after a tank of chemicals used for dyes exploded at a factory in central China.