Callous thieves caused commuter chaos on Wednesday morning after attempting to steal cabling from the Newbridge line overnight.
Signalling equipment was destroyed between Newbridge and Kildare which caused severe cancellations and delays to early morning traffic.
A spokeswoman for Irish Rail Jane Creegan told RTE's Morning Ireland that the attempted theft was discovered at around 5am when trains first started operaring.
Although the thieves were unsuccessful, they caused damage worth €4,000 worth of cable.
She said the automatic signalling system had to be switched to manual and as a result is currently leading to delays of up to 90 minutes.
Ms Creegan told Morning Ireland: "Engineers are on site replacing the cabling while a manual system is being used this morning."
"We hope to have the cabling system working again by mid morning, but it is unfortunate that the morning peak rush as been badly disrupted."
The theft of copper has become more common in recent years because of its increased value.
Thankfully, Jane told listeners that the service would hopefully be completely repaired before the busy evening commute.
For the moment, the Newbridge/Hazelhatch to Grand Canal Dock line is still impacted by delays while Heuston to Portlaoise is currently terminating at Newbridge.
As well as this, there is currently no Luas service between Blackhorse and the Point or Connolly.
Trams are only operating from Tallaght/Saggart to Blackhorse and Luas tickets are valid on Dublin Bus.
