Police officials said the incident took place at National Highway - 57 under Araria Town police station.
The tanker was coming from Forbesganj, while the auto-rickshaw was coming from the Purnia side.
Araria Town SHO Mukesh Kumar Sah said the deceased have not yet been identified, while the injured have been admitted to Araria Sadar Hospital. The bodies have been sent for post-mortem.