SINGAPORE - Two Americans are believed to be behind the vandalism of an SMRT train at Bishan Depot in 2011, according to self-released videos.

The two have been identified as Americans Jim Harper and Danielle Bremner, who go by the pseudonyms Utah and Ether.

A series of videos posted on their Facebook page and website between April and July show them vandalising trains in countries including Singapore, Thailand, India, Malaysia, Taiwan, Hong Kong, the Philippines, Turkey, Japan and South Korea.

According to Australian news reports, Harper was arrested in Melbourne in May this year on eight charges related to vandalism and assault and sentenced to six months jail. His partner remains at large.

In a statement to The Straits Times, the Singapore police said it is is aware of the arrest and is 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 in the case.

SMRT was fined $200,000 by the Land Transport Authority for the security breach in October that year. LTA said that SMRT had "failed to effectively guard against unauthorised intrusions and did not detect the Bishan depot breach quickly".

Additional security measures, including reinforced steel fences, were installed at SMRT's train depots following the incident.

A four-and-a half minute video on Utah and Ether's Facebook shows how two people and, presumably at least one cameraman, broke into the Bishan Depot by using wire cutters to cut through 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. The words match the grafitti in the case.

According to the website - www.utahether.com - Harper and Bremner have vandalised trains and walls across five continents.

They said their aim was to " challenge the viewer to confront traditional beliefs concerning personal and public property, and the social context of vandalism".

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 home towns, in 2008, for allegedly vandalising trains as early as 2005 .

But they broke the terms of their probation in 2011 by "boarding on a plane to India in 2011 and knowing they can never come back", said Utah and Ether on their website.

Their website gives their place of residence as Helsinki in Finland.

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

The first case was in May 2010, when two vandals cut through the wire fence and spray-painted the side of a train in Changi depot. Swiss national Oliver Fricker was given seven months' jail and three strokes of the cane, while Briton Lloyd Dane Alexander remains at large.

In May 2014, a train at Bishan depot was found with smeared with a red scrawl.

And just six months later, Germans Andreas Von Knorre and Elton Hinz sprayed graffitti on a train at Bishan Depot in the early hours of Nov 8. The men were sentenced last year to nine months jail and three strokes of the cane.

SMRT was fined a total of $250,000 for the two breaches in 2010 and 2011, and it vowed to strengthen security measures after the last incident.