Services on Dublin's new Luas line from Sandyford to St Stephen's Green were disrupted for between 30 and 40 minutes this morning because of a power cut.
A spokesman for the Rail Procurement Authority (RPA), the company which oversees the tram system, said an investigation into what caused the outage was underway.
He said the power cut occurred shortly after 6.00 a.m. but "interference was minimal" given the time of day.
The spokesman said arrangements for stand-by buses had been in place but in the end they were not needed.
