Five casualties have been taken to various hospitals in the Dublin Region.
The casualties include an adult male, an adult female and three young children.
One child, a girl, has sustained serious injuries, the other two children are being treated for less serious injuries.
An Garda Síochána is in contact with parents of all three injured children.
The adult female is being treated for serious injuries and the adult male for less serious injuries.
The scene remains sealed off at this time.
All lanes are currently closed and diversions are in place.
An Garda Síochána is following a definite line of inquiry and not looking for any other person at this time.
The incident took place outside Gaelscoil Coláiste Mhuire on Parnell Square East at around 1.40pm
There is no further information.
