The incident took place on the State Highway -73 near Khori Pakhar village as the speeding vehicle rammed into a truck from the opposite side, Amnaur police station in-charge Vinod Kumar said.
While four occupants of the vehicle died on the spot, two others sustained injuries, he said.
The victims were identified as Shahabuddin (35), Raj Kumar (50), Pancha Sah (40) and Phulmati Devi (35).
The bodies have been sent for post-mortem and the injured persons admitted to the Patna Medical College and Hospital (PMCH) in the state capital, the police officer said.