Gardaí have closed the Naas to Newbridge Road in Co Kildare due to a gas leak.
Motorists are being urged to avoid the area and major traffic delays are expected.
A spokesperson for Gas Networks Ireland said its emergency team are currently at the scene of a "large gas leak" after a mains was hit.
The R445 is closed to all traffic from junction 10 at Bundles of Sticks to Ladytown Cross.
Local diversions are in place.
Kildare County Council says the incident is expected to last for several hours and it is possible that it will be overnight.
Meanwhile, traffic is also heavy on the M50 southbound following a collision.
All three lanes are blocked due to a crash just before J16 Cherrywood.
More to follow...