Five years after an SMRT train in Bishan depot was vandalised with graffiti, the identity of the perpetrators has apparently been solved through a video they made.

Americans Jim Harper and Danielle Bremner, who go by the pseudonyms Utah and Ether, released a video online recently appearing to show them committing the act.

According to Australian news reports, Harper was arrested in Melbourne in May on charges related to vandalism and causing injury, and sentenced to six months' imprisonment, while his partner remains at large.

In a statement yesterday, the Singapore police said they are aware of the arrest and are currently working with the Australian authorities "to facilitate investigations into the case of vandalism reported at Bishan MRT depot in August 2011".

On Aug 17, 2011, a train at Bishan depot was found to have the word "Jet Setter's" scrawled on it, though the graffiti was noticed only after the train had been in service for several hours. No culprits were caught.

SMRT was fined $200,000 by the Land Transport Authority for the security breach in October that year.

A series of videos posted on Utah and Ether's Facebook page and website between April and July, titled Probation Vacation: Lost In Asia, show them vandalising trains in places, including Singapore, Thailand and Hong Kong.

The 41/2-minute video on Singapore shows how two people and, presumably at least one cameraman, broke into Bishan depot by using wire cutters to cut the fence. Two figures dressed in black and with their faces covered are seen crossing the tracks and spray-painting the carriage of a train with the words "Jet Setter's". The video also features Singapore news clips on the 2011 incident.

According to their website, Harper and Bremner have vandalised trains and walls across five continents.

They claim to have produced 20 short films and published four books, while their latest work, the 12-episode series Probation Vacation: Lost In Asia, documents their five years spent travelling across Asia.

According to the New York Post, the duo had been arrested in New York and Chicago, their hometowns, in 2008, for allegedly vandalising trains as early as 2005. But they broke the terms of their probation in 2011 by "boarding a plane to India in 2011 and knowing they can never come back", said Utah and Ether on their website.

According to The New Yorker, efforts are under way to extradite Harper to the US, where there are two arrest warrants for him. Bremner evaded Australian police on a flight bound for Hong Kong, it said.

There have been three other cases of vandalism at SMRT's depots since 2010, with two of these occurring at Bishan.

In the most recent case, Germans Andreas Von Knorre and Elton Hinz were sentenced to nine months in jail and three strokes of the cane for breaking into Bishan depot and vandalising a train carriage in 2014.

The Land Transport Authority said in a statement yesterday that it works closely with public transport operators to ensure security at train depots and commuters' safety. Additional measures have been taken to improve security, including increasing patrols at depots and upgrading perimeter fencing, it said.