The man holding up Southern Cross Station has been apprehended by police and is now safe.
It is believed trains will begin operating shortly.
Reports are claiming that a man is perched on the edge of a walkway at Southern Cross Station.
Police are in negotiations with the man.
The affected train lines are Craigieburn, Sunbury, Upfield, Cranbourne, Frankston, Werribee and Pakenham.
A police operation is underway at Southern Cross Station resulting in all train lines being suspended.
The network has been stopped since 3pm.
It is unclear at this stage what has caused the disruption, with police claiming a 'trespasser' is being negotiated with.
More to come.