One of the collisions resulted in a vehicle overturning onto its roof.
A woman has died and four people have been injured after two separate road crashes in Clare and Mayo.
The fatal two-car collision occurred at Liscosker, Kilkelly in Mayo on Saturday, 24 September at around 4pm and resulted in one of the vehicles overturning onto its roof.
Both drivers of the cars and five passengers were taken from the scene to Mayo General Hospital.
One female passenger in her 80s was in a serious condition following the crash and passed away on Tuesday, 4 October.
The rest of the drivers and passengers were released from hospital.
Gardaí are urging witnesses to the collision to come forward and are particularly appealing to motorists who may have stopped at the scene of the crash prior to the arrival of Gardaí and emergency services.
They have also asked motorists with any video footage, including dashcam footage, who were travelling on the N17 at Liscosker, Kilkelly on the Saturday afternoon to make contact with investigating Gardaí.
Anyone with information is asked to contact Swinford Garda Station on 094 925 2990, the Garda Confidential Line on 1800 666 111 or any Garda station.
An Garda Síochána are also appealing for witnesses following a crash that took place in Newmarket-on-Fergus in Clare on Wednesday, 5 October at 6.10pm.
The two-vehicle collision occurred on the R458 in Drumline and the three male occupants from one car were taken to University Hospital Limerick.
The condition of one man, aged in his 20s, is described as critical. The two other men continue to receive medical attention.
Meanwhile, the driver of the second car, a woman in her 60s, was also taken to University Hospital Limerick with non-life-threatening injuries.
Gardaí are appealing to any person who may have information in relation to this collision to contact them.
Any person who witnessed the collision is urged to come forward and any road users with video footage, including dashcam footage, are asked to make this available to investigating Gardaí.
Anyone with information can contact Shannon Garda Station on 061 365900 or the Garda Confidential Line on 1800 666 111.
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