The accident happened in Fengcheng at around 7 a.m. (2300GMT), and rescuers are on the scene Xinhua said, without giving other details.
Deadly accidents are relatively common at industrial sites in China, and anger over lax standards is growing after three decades of swift economic growth marred by incidents from mining disasters to factory fires.
China has vowed to improve safety at such facilities. President Xi Jinping has said authorities would learn the lessons paid for with blood after chemical blasts in the port city of Tianjin last year killed more than 170 people.
