Commuters suffered disruption after cable thieves targeted the Metro system for three consecutive days.
The system was first targeted on Saturday afternoon at East Boldon, South Tyneside.
Trains were cancelled between East Boldon and the Stadium of Light from 2.30pm until 6pm due to missing cable.
On Sunday, 100m of cable was taken from Percy Main, in North Tyneside.
The theft affected trains between Tynemouth and Whitley Bay until 6pm.
Yesterday morning saw rush hour commuters making the journey between North Shields and Byker, Newcastle, by bus until 10am after 30m of cable was stolen from Wallsend.
But now Metro bosses have warned cable thieves their actions will not be tolerated.
Ken Mackay, director of rail and infrastructure for Nexus, said: "The true cost of cable theft is not the amount we must pay to replace cable, which is often very small, it is the cost of providing replacement bus services or paying other companies to accept our tickets and the cost to our passengers of being late for work or missing important appointments.
"In most recent incidents we have actually been able to repair damage before it causes significant disruption to our passengers, but sadly in some cases this is not possible and I am sorry for the inconvenience this causes.
"But we can promise passengers we are doing all we can to combat this problem." Nexus works closely with police to identify hotspots for theft then increase patrols in the area.
It also uses its own staff and security companies to increase the human presence along sections of track where modernisation work is currently taking place.
At the weekend there were increased patrols including rail vehicles going back and forth along stretches of line where passenger trains were not running.
Engineers worked for hours at a time repairing damage and also operating track points and signals manually to keep trains running.
Nexus is also devising community campaigns warning of the dangers of cable theft.
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