Metro services have been suspended again on Sunday after the theft overnight between Wallsend and Monkseaton.
It follows incidents on Friday January 5 and 6.
Nexus, which runs the Metro, issued a £1,000 reward on Thursday for information leading to prosecution of the cable thieves.
The provider also said it is stepping up overnight patrols to deter criminals.
In a statement, Northumbria Police said: “This type of behaviour will not be tolerated and officers are continuing to carry out regular checks across the system alongside Nexus.
“Anyone with information should contact police via the ‘Tell Us Something’ page of our website or by calling 101, quoting log number NP-20230106-0038.”
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