The accident took place around 5 am when the van was hit by a paddy-laden truck on National Highway 31 in Pothia outpost area, additional inspector Sanjay Singh said.
He said the driver and helper, Abdul Hamid (50) and Rakesh Pandit (22) respectively, died on the spot while 28- year-old Army jawan Adarsh Kumar succumbed to his injuries while being taken to a hospital.
Both Pandit and Kumar hailed from Begusarai district while Hamid belonged to Hamirpur in adjoining Uttar Pradesh.
The Army jawan had hired the van at New Jalpaiguri in West Bengal, where he was posted, for a journey back home on a vacation, the police officer said.
The driver and other occupants of the truck fled the spot after the collision. Both the vehicles have been seized.