PARIS - An explosion at a grain silo rocked the eastern French city of Strasbourg Wednesday morning, injuring four of the 11 people on the scene, the French television channel BFMTV reported, citing an anonymous source of the National Police of France.

Three among the four injured are in critical condition, radio network France Bleu Alsace reported, adding that the cause of the blast has not been identified.

Some 70 firefighters have rushed to the scene of the explosion, which caused a large plume of smoke and a fire, the radio network quoted local authorities as saying.

The explosion probably took place in a warehouse for agricultural products of a company named Silostra Silorins, and access to roads leading to the affected area has been barred, a local traffic information association said.