A Sept. 15 accident at a Sinopec plastics factory in Zibo, Shandong province killed five workers. The victims include one plastics factory worker and four construction workers - including the project manager -- from a construction company also under the Sinopec umbrella.

According to a spokesman from Sinopec Qilu Petrochemicals Co. Ltd., which owns the plastics factory, a burst of nitrogen gas from a pressurized tank killed the workers -- two died on site, three more later in the hospital. In addition, one worker sustained a minor injury.

While the incident is under further investigation, the company said preliminary findings point to work performed against regulation.

"Some screws on the gas container might have become loose, or workers failed to turn down the gas pressure before fixing the screws," the factory's deputy director Zhao Yanbin told the Xinhua news agency.

The plastic factory contracted with Sinopec Qilu Petrochemical Construction Co. Ltd. to replace a heat-exchange unit, state enterprise Sinopec said. It noted that this particular construction subsidiary branched out in a restructuring and now has private and collective ownership.

Sinopec Qilu Petrochemical also was forced to shut down one furnace at an 800,000-metric-ton-per-year ethylene plant on August 26 due to a small fire caused by oil leak.