Eircom has said the theft of copper wire has become an issue for the company.
It follows the suspension of DART services in Dublin this morning because of the theft of signal cable.
Rail services between Bray and Dalkey were cancelled for a time following the cable theft in the Shankill area.
Iarnród Éireann spokesperson Barry Kenny said this type of theft was unusual but not unprecedented.
He said the material that was taken had an electrical current going through it and the thieves were lucky not to have been killed or seriously injured.
Meanwhile, Eircom said it has had 20 incidents of metal theft so far this year, with copper wiring worth over €20,000 being taken.
Last year, the company said there were 200 incidents of metal theft; with 60,000 metres of cable valued at €240,000 taken.
In a statement the company said these thefts do result in loss of service to customers.
They urged anyone with information about them to contact gardaí.
A spokesperson for Veolia Transport, the company that runs the Luas, said there had been a small number of thefts of cable wires over the last number of months.
She said replacing the cables cost a "significant" amount although caused no disruption to travel.
The spokesperson warned of the potentially dangerous consequences of stealing cable wires, saying the wires are live and of high voltage.