Transport Canberra deputy director general Duncan Edghill said the light rail vehicle was able to continue its journey once its software had been rebooted.

He said it appeared to be an isolated incident and was not aware of any other breakdowns since the service launched on Saturday.

Passengers on a 9.30am service from Gungahlin to the city were left trapped inside the carriage, Liz Allen, who was on board, said.

Dr Allen said the power cut in and out four times between when she got on at Nullarbor Avenue and when she got off at the city.

"We had an announcement from the driver that the power had been lost to the overhead wires," Dr Allen said.

"He apologised and said they didn't know how long the delays would be.

"The tram would sound like it was powering up and we'd move on. [It] probably powered down and up again maybe four times."

The tram first broke down when the service reached Mitchell, Dr Allen said.

She said she boarded the light rail just after 9.30am and reached the Alinga Street station in the city just before 10.30am.

Dr Allen said airconditioning on the light rail vehicle also was cut during the breakdown.

"Most of the ride was without air con. There were no seats and very little room," Dr Allen said. ".. A bunch of very angry people were getting off."

On Tuesday afternoon, Mr Edghill said technicians were working through the cause of the breakdown, but overall the system had performed "spectacularly" since its launch.

"At this early stage it looks like it may have been a software issue with that vehicle, where the vehicle was effectively rebooted and was able to continue through its journey," he said.

"With any new bus or light rail vehicle there are some teething issues that may need to be worked through."

Dr Allen said the breakdown had a flow on effect to other services with other trams facing queues to access stops along the route.

The breakdown comes just days after the light rail was opened to the public, with more than 25,000 people riding the service on its first day on Saturday.

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