The N3 in Co Cavan is closed in both directions between Butlersbridge and the turn off for Deredis.
It follows a road traffic collision at Drumhirk that involved three vehicles.
Local gardaí say are unaware if anyone was seriously injured in the crash.
Diversions are in place via the Old Butlersbridge Road.
It's not known when the road will re-open and the Fire Service, Gardaí and Ambulance Service at scene.