At least five people have been killed after a chemical plant explosion on Thursday, Xinhua quoted government sources of Wucheng county in east China's Shandong province as saying. The accident occurred at 3:30 p.m. in the Heli Chemical Company in Wucheng County when a facility was in trial operation. The blast left the trial operation director dead on the spot, and injured 13 others. Four others died later in hospital. One of the rest nine injured was hurt severely and received operation. Initial investigation showed all the dead and injured were migrant workers in the same province. Further probe has been started for the cause.