Mufassil police station SHO Krishnandan Verma said the incident took place around 5 AM today due to dense fog.
The driver could not see the stationary 18-wheel truck and rammed into it from behind near Ora village under the jurisdiction of Mufassil police station of the district.
The car was hit by another truck from behind and the occupants got sandwiched between the two heavy vehicles, Verma said.
The sole seriously injured person was referred to Varanasi, in neighbouring UP, for treatment, the SHO said.
The deceased have been identified as Dipak Kumar, Jitendra Singh, Krishna Singh, Sita Devi and Kajal Kumari.
All the deceased persons, residents of Chenari area of Rohtas district, were returning home after attending a marriage ceremony in Dhanbad in Jharkhand.