Melburnians are being urged to call triple zero if they see people climbing aboard moving trains after a video emerged of two teenagers train surfing in broad daylight.
In the YouTube video, which was published in early October, two youths dressed in black climb onto a train along the Belgrave line just before it arrives at Camberwell Station.
The teenagers dangle from two carriages despite the possibility of being struck by a train coming the other direction.
When the train slows down and reaches the station, the youths jump onto the platform, startling the passengers waiting for the train's doors to open.
Metro spokeswoman Sammie Black said the video displays "extremely dangerous and risky behaviour".
Ms Black confirmed Metro is investigating this particular incident.
"We ask our customers if they witness train surfing stunts to call triple zero or press the red emergency button on train carriages or on platforms," she said.
"We also have authorised officers across the network, a dedicated security and surveillance team who investigate every incident and we work closely with police to stamp out train surfing."
A group that calls themselves the Sky High Idiots has claimed responsibility for the stunt.
Two youths have filmed themselves risking their lives hanging off the side of a Melbourne train. #7News https://t.co/DieoCpflm0
— 7 News Melbourne (@7NewsMelbourne) October 12, 2016