A woman in her 50s is being detained by Gardaí this evening following a serious collision near Newtownforbes, Co. Longford.
The woman involved was the driver and only occupant of a car that collided with another car at Lamagh shortly before 3pm this afternoon.
A person in their 20s, who was driving the second car, was airlifted to hospital and it's understood he sustained head injuries.
The N4 has been closed at Lamagh while the scene is examined.
Gardaí are asking anyone who may have witnessed the collision to contact them.