Authorities confirmed on Thursday that the shiny red tram had been "targeted by graffiti vandals" on Wednesday evening, having been brought into the capital under cover of darkness with a police escort about 2am that morning.

Before the vandalism, it is understood at least two security guards as well as sensor lights were in place to guard the tram.

But by Friday morning such measures had been stepped up to include cameras and double fencing.

"A small amount of graffiti occurred on Wednesday night and it has now been removed," a Transport Canberra and City Services spokeswoman said on Friday.

"The police have been notified."

Canberra Metro chief executive Glenn Stockton called the vandalism disappointing.

"Of greater concern is that members of the community have accessed a live construction site, which puts them and others at risk," he said.

ACT policing confirmed officers were investigating the vandalism.

"The investigation is ongoing and the facts are yet to be established," a police spokesman said.

The ACT government has not yet said when it will officially unveil the tram, the first of 14 slated to run on the 12km city to Gungahlin corridor when it comes online in late 2018.

On Thursday afternoon, the graffiti was removed at a "modest cost" to Canberra Metro.

The government is spending $65 million on the fleet, with each tram 33 metres long and able to carry 207 people.

A video of the first tram leaving Spain for a seven-week journey to Australia was posted on YouTube in November.

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