The Sydney morning rush hour was thrown into chaos on Monday, with multiple train lines impacted by urgent repairs, delaying thousands of commuters.
The T1 North Shore and Western Line, T2 Inner West and Leppington Line, T5 Cumberland Line and T7 Olympic Park Line have been impacted.
Urgent signal repairs were required at Harris Park, according to Sydney Trains.
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Services on the T1 line and T2 line continue to be disrupted.
Services may be less frequent, trips may take longer than usual, and stops may change at short notice.
The T5 line was not running for some time, with services resuming about 11am.
Services are now running at a reduced frequency, and commuters may need to change at Granville or Lidcombe to complete their journey.
Trains were running at a reduced frequency on the T7 line between Lidcombe and Olympic Park, but on late Monday morning were returning to normal.