Gardaí have renewed their appeal for information on the fatal crash that occurred on Thursday evening on the M6 at Poolboy, Ballinasloe.
Four people were pronounced dead at the scene and their bodies were removed to Portiuncula Hospital, Ballinasloe, for post mortem examinations.
As of Friday evening, no formal identification of those who died has taken place.
It is understood that an infant and their parents are among those who died at the scene, while the driver of another car was also killed.
The single-occupant vehicle is believed to have travelled the wrong way down a slip road onto the motorway before driving into oncoming traffic for some distance.
A technical examination of the scene has been completed and the road has now reopened fully.
Gardaí are appealing to any road users who may have camera footage including dash-cam and were travelling on the M6 at Poolboy, Ballinasloe, between 7.20pm and 7.50pm, to make this footage available to Gardaí.
Anyone with information is asked to contact Ballinasloe Garda Station on 090 9631890, the Garda Confidential Line on 1800 666 111, or any Garda Station.