The bridge collapsed when a 10-wheeler goods-laden truck was passing through it, a transport department official said, adding that the structure was in a fragile condition since last night.
This has left around 200 goods-laden trucks coming from Jiribam town to Imphal stranded. Repairing works are being carried out on war-footing, the official said.
The Barak bridge is located along the Imphal-Jiribam highway and passes through the hill district of Tamenglong.
The highway, considered as the second lifeline of the border state, assumed greater importance after a massive landslide at Viswema in neighbouring Nagaland cut off the major Imphal-Dimapur national highway.