The N2 is now closed both ways at Castleshane Hill about 5km outside Monaghan Town due to a collision, AA Roadwatch are reporting.
Gardai are at the scene and diversions will be in place. Traffic is busy on this stretch.
It is thought that a person has been hurt in the crash.
AA roadwatch posted on Twitter: " Monaghan. N2 closed due to crash."
Meanwhile, the N21 remains closed in both directions outside Rathkeale in Limerick on the Croagh side as Gardai continue to deal with a crash.
Traffic is quite slow on approach both ways.
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