At least five spans and four pillars of the bridge caved in around 8.30 pm when around 30 labourers were working at the spot.
Official sources said at least 21 labourers and a junior engineer sustained injuries in the mishap and they were rushed to the nearby hospital.
Three seriously injured labourers however, were shifted to the SCB Medical College and Hospital here and stated to be out of danger.
Work on the 2077 meter Jatamundia-Sonepur Bridge over Mahanadi was undertaken in 2008 to establish a link between the Banki and Athagarh sub-division of the district. While the R&B division of the Works department is executing the work, the construction of the bridge is handed over to a private construction company.
While the initial estimate of the bridge was pegged at Rs 54 crore and was to be completed by the end of 2011, the revised estimate has crossed over Rs 62 crores and the revised deadline of its completion has overstepped by over eight months.