Two people have been brought to hospital with suspected spinal injuries after an early morning crash between a Luas and truck.
Six units of Dublin Fire Brigade attended the scene on the Cheeverstown section of the Luas red line this morning.
The service is not running between Saggart and Belgard.
AA Roadwatch said: "Following an incident involving a Luas and a truck, the Red Line is not running between Saggart and Belgard and will only operate between Tallaght and the Point."
The company that runs the Luas confirmed tickets are valid on Dublin Bus and a Dualway coach also in operation.
All Green Line services are operating normally while all lifts and escalators are in full working order.