Thirteen people have been confirmed dead and 20 others remain missing after a blast ripped through an explosives manufacturing plant in East China's Shandong Province on Monday morning, sources with the rescue headquarters said on Tuesday.

The explosion, which occurred at 10:45 am inside a three-storey workshop of a plant owned by the Jinan-based Poly Explosives Company in Caofan township, Zhangqiu, also injured 19 people.

The injured are being treated in three hospitals in Zhangqiu and neighboring Jinan, capital of Shandong Province, according to rescuers.

As of late Tuesday, all the injured who were  hospitalized were stable.

By noon on Tuesday, search and rescue work for the missing people was still continuing and rescuers had started to clean up the site.

Local police have also launched a DNA identification database to help check the casualty numbers, said Liu Xinyun, director of the municipal public security bureau of Jinan, which administers Zhangqiu.

With a history of 55 years, the company, which is now owned by the State-owned China Poly Group Corporation, is a professional manufacturer of civil explosive materials.

Covering an area of 66 hectares, the company's plant in Caofan township was a new manufacturing base with an annual output of at least 30,000 tons of explosives, according to the company's official website.