UPDATE from Gardai 3.01pm.
The bridge has now reopened to traffic.
However, the gardai report it is moving slowly.
Diversions are no longer required but motorists may wish to still avoid the area.
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Gardaí are advising motorists that Carrick on Shannon Town Bridge in Co. Leitrim is currently blocked due to a broken down HGV.
Diversions are in place and traffic is asked to avoid the area.
Gardaí say the road is likely to be closed for approximately three hours.
Eastbound Traffic on the N4 from Sligo should divert at Boyle.
Westbound Traffic on the N4 should divert at Longford.
Traffic that has already passed Boyle can divert at Cootehall.
Traffic that has already passed Longford can divert onto Leitrim Road (via Carrick on Shannon Town).