The N5 is closed to traffic outside Castlebar following a serious collision between a lorry and a car.
Gardaí and emergency services are at the scene of the incident, which occurred at around 10am near Windsor.
Midwest News understands that there was one occupant in each vehicle.
One of the individuals is being dealt with at scene, while the other was taken by ambulance to Mayo University Hospital.
Local diversions are in place in between Castlebar and Turlough at the point of the collision and it is expected that the road will remain closed for a number of hours.
Gardaí say investigations into the incident are ongoing and are urging anybody who was in the area this morning that may have seen the incident or who has dashcam footage to contact Castlebar Garda Station on 094 903 8200.