HARBIN - Some people might have brought explosives onto a commuter-van whose explosion Friday killed seven people and injured 40 others in Northeast China's Heilongjiang province on Friday, a police probe showed Saturday.

An initial investigation by the experts from the Ministry of Public Security showed that there might be explosives on the vehicle at the time of blast in Shuangyashan City, the city government said Saturday. Further investigation is still going on.

The commuter-van from a mine company in Shuangyashan exploded around 6:30 am Friday in the city's Lingdong district. The explosion affected a coach on the opposite lane.

Seven of the 52 passengers aboard the two vehicles were killed at the scene. Further 40 were injured, including seven in critical contidions.

The Zhongxing Mineral Industry Company, which owns the commuter-van, is a private enterprise.