One man died and 11 people were injured in a St Patrick's Day crash in the midlands.
One of the injured was said to be fighting for his life last night in Dublin's Beaumont Hospital after being airlifted from the scene.
The man who died was in his 60s, gardai said as they continued to investigate the circumstances.
He was pronounced dead at the scene, while the female passenger in his vehicle, who is also in her 60s, was taken to Midland Regional Hospital in Mullingar.
Nine other people were being treated for various injuries following the five-car pile up on the M6 motorway near Kilbeggan in Co Westmeath.
Gardai said four drivers and five passengers of the other vehicles involved were taken to the Midland Regional Hospitals in Mullingar and Tullamore, where they were being treated last night for various injuries.
The pile-up happened just beyond junction 5 eastbound near Kilbeggan.
Members of the Garda Technical Bureau carried out a forensic examination of the scene yesterday afternoon, while forensic collision investigators carried out their own enquiries.
A garda spokesman said a file will be prepared for the local coroner and that anyone who may have witnessed or has information relating to the crash should contact local officers.
"Gardai in Athlone, Co Westmeath, are appealing for witnesses following a fatal road traffic collision today, March 17, 2019," the spokesman said.
"A report has been sent to the local coroner and the scene is preserved for examination by garda forensic collision investigators. The stretch of road remains closed
"Anyone with information is asked to contact Athlone Garda Station (090-6498550) or the Garda Confidential Line (1800 666 111)."
The crash brings to 36 the number of people who have died on Irish roads so far this year.
Earlier this month, gardai and the Road Safety Authority (RSA) raised concerns about the increase in traffic fatalities compared with last year, which was Ireland's safest 12 months.
"Road deaths have increased by nearly 30pc in 2019. This upward trend must be addressed immediately," gardai said in a statement.
In a separate incident over the weekend, a man in his 60s died following a collision near Swinford, Co Mayo.
The collision, which happened on Friday afternoon, involved a truck and two cars and resulted in the death of the 64-year-old driver of one of the cars.
He was taken from the scene to Mayo University Hospital in Castlebar for a post-mortem to be carried out.
The male driver of the second car suffered minor injuries.