Metro passengers faced disruption on Thursday morning after five trains had to be taken out of service - one of them due to vandalism.
Four trains had to be halted due to developing faults and one was removed after it was vandalised at the Howdon depot.
A person got onto the site in the early hours and smashed one of the Metro train's windows. The matter has been reported to the police.
READ MORE: Vaccinated holidaymakers could be allowed to travel to amber countries without quarantine
Nexus, which operates the Metro network, says all the services that were cancelled were extra ones they run during the morning peak travel periods between Pelaw and Regent Centre/Monkseaton, from 6am to 9am.
However the core service, consisting of 28 trains, was unaffected.
A Nexus spokesperson said: "We apologise to customers who were inconvenienced by the cancellation of five of our peak time services on Thursday morning.
"These are the extra trains that we operate between Pelaw and Regent Centre/Monkseaton to give us extra capacity in the busiest central part of the network through Newcastle city centre and Gateshead. Our core service was unaffected.
"Four of the trains were taken out of service due to developing faults. It is a reminder as to why we are investing in a new fleet of Metro trains, which is set to start entering passenger service in 2023.
"The new trains will transform the experience for customers, and deliver a step-change in quality and reliability.
"One other train was not fit for service this morning after it was vandalised overnight at our Howdon depot in North Tyneside.
"The offence has been reported to the police and we will be checking CCTV to support them. This was an act of criminal damage and anyone who gets caught doing this will be prosecuted."
