Five gunmen stopped the cash van and looted Rs 70 lakh from bank officials at gun-point, the police said.
They also looted two rifles from the homeguards in the cash van, the police said.
They later escaped with the cash van after asking the officials and homeguards to disembark from the vehicle.
The money was being taken to Sonepur branch of the bank from Hajipur, the police said.
All the entry and exit points of the district have been sealed and massive raids were going on to apprehend the looters, the police said.