Police say they are looking into a video showing a man jumping from platform to platform at an MTR station.
Footage circulating online appears to have been taken by the man himself as he leapt over the train track at Fo Tan Station on Saturday night.
The MTR Corporation called in the police on Monday night after reviewing its CCTV footage.
The company said the two platforms involved are more than two metres apart.
Police said the man carrying out the stunt appears to be between 20 and 30 years old, while CCTV suggests another man of around the same age also filmed what happened.
Officers said the case has been classified as a breach of MTR by-laws. No arrests have been made.