A metal object left on overhead train wires near Loftus has caused long delays on the Eastern Suburbs and Illawarra line and South Coast lines today.
Sutherland police are investigating how the metal object, possibly a bike chain, was left hanging on wires when the train came into contact with it at around 1.30am.
The obstruction forced the train to automatically emergency stop causing significant damage.
Repairs were carried out for several hours disrupting peak hour services.
Police said the cost for repairs is significant.
Anyone with information is urged to call Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page: https://nsw.crimestoppers.com.au/
Police said people can remain anonymous.