The accident happened near Dumduma bridge under the jurisdiction of Kalyanpur police station.
The SHO of Kalyanpur police station, Amjad Ali said that the jeep's driver Mithu Mandal died on the spot while two other persons travelling in the ill-fated jeep died while they were being treated at Samastipur Sadar hospital.
They were identified as Ganga Sahni and Kailash Sahni.
The other two seriously injured persons were undergoing treatment at the Sadar hospital, he said.
He said that they were returning to their village after making purchases from Samastipur for a marriage that was scheduled on May 10.
The police seized the bus and arrested the driver, the SHO said.