"These contractors not only violated the agreement, they also ignored government's repeated request to speed up work and failed to complete it," Yadav said.

The department has blacklisted contractors who include Shambhavi Engineers of Andaman Nicobar, D.K. engineering of Siliguri, and Lanco Infratech of Hyderabad.

The contractors would not be allowed to participate in any tenders for road construction in future, said an official from the road construction department.

The contractors were engaged in road construction work under various schemes in the state, the official said.

Till a few years ago, Bihar was notorious for its poor roads, even state and national highways. For the past six years, the Nitish Kumar-led state government has accorded priority to construction of roads.