Gardaí and emergency services have been at the scene of incident on the M50 northbound between Junction 9 Red Cow and Junction 7 Lucan since before 2pm.
Traffic queued up between the Red Cow and was allowed to get past the collision scene, but all northbound lanes were then closed again, with motorists advised to avoid the M50 if at all possible and use diversions as the northbound section will remain closed for several hours.
In a statement posted on Twitter this evening, gardai said: "An Garda Síochána is aware of graphic images of today's Fatal Road Traffic collision which are being shared across social media and messaging apps. An Garda Síochána appeals to everybody, DO NOT SHARE This Material, it is disrespectful to the deceased, their family and friends!!"
Meanwhile, Investigators are appealing for any witnesses to road traffic collision to come forward.
Any road users who may have camera footage (including dash-cam) who were travelling on the M50 Northbound before Junction 9 prior to the road being closed or any road users who may have passed the scene should to make the footage available to Gardaí.
The motorway remains closed between Junction 9 and Junction 7 with diversions in place as Gardaí investigate the incident.
Gardaí are advising all road users to avoid the area if possible as traffic is currently extremely congested.
Gardaí are also advising all road users on the N7, intending on travelling on the M50 Northbound to avoid the area or take alternative routes if possible.
Traffic is extremely heavy on both sides of the M50 with emergency services now rerouting stationary traffic to exit at J9 and follow diversions. The tailback of traffic on the northbound section of the motorway extends for several kilometres, with long delays on the southbound section also.
M50 management team said traffic stuck between J9 Red Cow and the collision is now being allowed past the collision on the hard shoulder and auxiliary lane.
The team said their thoughts and prayers were with the families of all involved.
One motorist who was driving southbound this afternoon shortly after the collision occurred, said: “The tailback went on and on for what seemed like forever. I've never seen so many cars in my life.”
A spokesman said earlier: "Gardaí are currently at the scene of a serious RTC on the M50 northbound.
"The road is currently closed between junctions 9 and 7 northbound with diversions in place. Gardaí are encouraging all road users to avoid the area if possible."
Dublin Fire Brigade tweeted: “We're currently attending a serious road traffic collision on @M50Dublin J9 Red Cow Northbound. All lanes are closed at present. Motorists are advised to follow the diversion route from J9 Northbound back to J7.”
Meanwhile, traffic reports have said the M50 Southbound is also extremely slow from the M1 to Cloverhill Bridge.