Two suspects of the explosion in North China's Shanxi Province that killed 31 on Monday, surrendered to police yesterday.

Wang Jinsheng(C) is taken to the site where the blast occured. [sina]

The accident was caused by the explosives Wang Jinsheng and Wang Guohua had stored illegally in a garage of the hospital, according to local police.

The local public security department posted a nationwide reward of 100,000 yuan (US$12,330) in an attempt to find 41-year-old Wang Jinsheng, the prime suspect who worked with the staff hospital of the Xuangang Coal and Electricity Company in Yuanping.

He had the key to the garage for job purposes.

He disappeared after the explosion on Monday.

Wang was in Shuozhou, north of Shanxi Province, when he gave himself up yesterday.

It is reported that Wang used to run a coal mine. The explosives were possibly left after the mine was closed.