The incident took place last evening and nobody was injured as the workers and officials had left for the day.
The Rs 7 crore bridge, located at Katra-Kevatsa route in Aurai block of the district was supposed to provide a stable road link to 15 panchayats populated by over 1 lakh people, which get cut-off from the district headquarters during the monsoon due to swirling rivers.
The project is a brainchild of Bihar Rajya Pul Nirman Nigam (BRPNN) and was being constructed with the help of NABARD.
The site where the bridge was located is not a defined river and the construction was being done by taking into consideration 7-metre depth of water, BRPNN Muzaffarpur Project Engineer B K Singh said.
"Our estimate is that more water came to the stream this time from different routes. It was unexpected, and hit the pillar from an angle. It could have collapsed due to the pressure of water," said Singh.