The Ring Road at Enfield in north Co Kildare (part of the Old N4 route) is closed following a collision.
Photos sent to KildareNow show that at least two vehicles were involved in the incident.
Debris can also be seen lying on the road.
AA Roadwatch said that traffic is very busy through the town as a result, with the queue back before the Newtown turn-off.
Gardaí have advised motorists to take the M4 as an alternative route.
Subscribe or register today to discover more from DonegalLive.ie
Buy the e-paper of the Donegal Democrat, Donegal People's Press, Donegal Post and Inish Times here for instant access to Donegal's premier news titles.
Keep up with the latest news from Donegal with our daily newsletter featuring the most important stories of the day delivered to your inbox every evening at 5pm.