Motorists have been advised avoid the M50 Northbound due to a "serious" crash around the Ballymun junction.
Emergency services including the Fire Brigade and the Gardai are attending the scene of the incident.
The section of road in between junction four and five has been closed and there are diversions in place for airport-bound traffic.
Dublin Fire Brigade tweeted: "Along with M50 Dublin services we're attending a serious road traffic collision at J4 Ballymun Northbound. Lanes are temporarily blocked, delays on approach."
The Gardai tweeted: "Dublin Traffic: The M50 Northbound is down to one lane of traffic between Junctions 3 and 4 due to a collision in the area. Expect delays. Motorists are advised to take alternative routes where possible."
They added: "The M50 Northbound is currently closed between Junctions 3 and 4. Traffic between Ballymun and Dublin Airport is being diverted."
TII tweeted: "Collision on M50 between J04 - BALLYMUN and J03 - M1/M50 (North) Lanes affected: Hard Shoulder, Aux Lane, Lane 1, Lane 2, Central Median (06-Feb 16:37)."
A spokeswoman for the Gardai said: "Gardaí and Emergency Services are currently at the scene of a road traffic collision on the M50 that occurred at approximately 5pm this afternoon.
"No further details are available at the moment."
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