JINAN - 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-story terraced workshop of a plant owned by Poly Explosives (Jinan) Co Ltd. in Caofan township, Zhangqiu city, also injured 19 people.

The injured are being treated in three hospitals in Zhangqiu and Jinan city, capital of Shandong province, according to the headquarters.

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

Police have also launched DNA identification to help check the casualty numbers, said Liu Xinyun, director of the Jinan Municipal Public Security Bureau.

With a history of 55 years, Poly Explosives (Jinan) Co Ltd, 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 was a new manufacturing base with an annual output of at least 30,000 tons of explosives, according to the company's official website.