The mishap occurred when the driver lost control of the trailer-truck which hit people in the procession, Giridih Deputy Commissioner Uma Shankar Singh said.
While some died on the spot, the injured were rushed to hospitals, police said.
"Eight persons died on the spot, two at Bagodar Hospital and one each at Dhanbad and Hazaribagh hospitals," district Civil Surgeon S Sanyal said.
Chief Minister Raghubar Das has expressed grief over the incident and announced an ex gratia of Rs one lakh each to the kin of the deceased.