Both occupants of the vehicle were transferred to the Midlands Regional Hospital in Mullingar, where a man remains in a serious condition.

Local diversions are in place as Gardaí conduct a Forensic Collision investigation.

The crash took place after 8 o’clock this morning and motorists are urged to expect delays if using the route.

The incident involving a truck and jeep has lead to tailbacks in the Sligo direction.

The project would consist of a mixed use development of commercial, office, retail, leisure and medical units.

The 52km section of the N4 passes through or close to several towns and villages including Ballinalack, Rathowen, Edgeworthstown, Longford and Newtownforbes.

It's understood it is a multi-vehicle incident.

Gardaí are appealing to anyone who witnessed the collision or who was traveling on the N4 in the Aghadegan area.