Irish Rail says the line has re-opened at Kildare with all services operating but subject to delays.
It comes after a person died following an earlier incident involving a train at Kildare Railway Station. Severe disruption hit services out of Heuston Station in Dublin because of delays on the line.
Irish Rail said the 10:00 service from Heuston to Cork struck and fatally injured the person at Kildare.
The 10:15 Heuston to Waterford service operated as a bus transfer from Newbridge, while the 08:55 Limerick Heuston service operated as a bus transfer from Monasterevin.
Iarnród Éireann has apologised for any inconvenience caused.