At least 20 workers were killed, two injured and nine missing after an explosion at the Yantai Zhaoyuan 761 Company in eastern China's Shandong province late Saturday, Xinhua news agency reported.

The plant handled the packing of explosives, it said.

Rescue workers were still searching for the nine missing employees, the report said.

Local officials in Xiadian township, where the factory was located, refused to comment on the blast, while phone calls to the company went unanswered.

Investigations into the cause of the explosion were ongoing, the report said.

In a separate report, Xinhua said that eight workers were killed and one other was reported missing after a explosion rocked the Wannianhong firecracker factory in northern China's Shanxi province on Saturday.

The cause of the accident was under investigation, it said.

Work safety standards are at notoriously low levels in many Chinese industries as companies try to keep up with rising demand caused by rapid economic growth.

According to the work safety administration, 15,396 people died in 12,800 industrial, mining and commercial accidents last year.