Update 9pm: Luas services in Dublin are now back operating normally.
It follows serious disruption on the green and red lines due to a system fault.
Luas operator Transdev has apologised for the inconvenience to passengers.
Earlier: System fault blamed for significant delays on Luas
There are significant delays on both Luas lines in Dublin this evening due to a system fault.
Luas tickets for the red and green lines are valid on Dublin Bus services.
Passenger Information Displays are also down, preventing announcements being made at stops.
#Luas Realtime forecasts on App and Website are now back in operation and are forecasting times system wide. We hope this will assist you, please again accept our apologies for any and all inconvenience— Luas (@Luas) February 12, 2018
Technicians are on site working to resolve the problem.
"There is what I would call a systems problem which is preventing us from updating the passenger information display which tells customers when the next tram is due," said Transdev's Dervla Brophy.
"The other thing that's happening is that we're not able to make announcements at the stop. The ticket vending machines are affected as well, and so too are the validators, where you touch on and off your Leap card.
- Digital desk