Armed Naxalites shot dead supervisors - Sunit Kumar Chaube and Dinesh Kumar Yadav - and injured their driver Kishore Yadav of Pratistha Construction company, sources said.
The injured driver was taken to a hospital in Gorakhpur, they said.
A leaflet of Bihar People's Liberation Party demanding extortion has been received from the spot, the sources said.
The construction company was building a bridge on the Narayani Gandak river to connect Mangalpur village with Bettiah in West Champaran district.