Part of the Metro line was closed this afternoon after grit was said to be the cause of a track fault.
Commuters faced longer journeys this morning because of the Network Rail track circuit fault at East Boldon, before the section of line between Brockley Whins and East Boldon was closed off in both directions due to issues.
A bus service was put on between East Boldon and Heworth, with passengers warned the journey could take an hour.
The trains were back in action shortly after 12.30am, with Metro thanking people for their patience.
A Metro spokesman said: "The problem affected all train services between Newcastle and Sunderland.
"Network Rail, which owns and maintains the railway line, suspended all services while they repair the fault at Boldon Lane Level Crossing, which is also closed to road traffic.
"As a result, we operated a service between East Boldon and South Hylton, and from Brockley Whins to all other stations going north.
"We had some buses between Heworth and East Boldon to carry passengers across the gap.
"We understand this was caused by road salts and grits getting into the circuit around the level crossing, which is causing the signals to turn to red.
"This morning, trains had to be talked past the signals at very slow speed.
"Metro had to cancel some services and the other services were going through at very slow speeds, adding 10 or 15 minutes to the journey times.
"The problem started at about 6.45am, and it was at 11.55am that Network Rail made the decision to take the line down altogether."
Earlier today, the service said people would have an extended journey time of approximately 15 minutes, with every third train may not likely to run due to the nature of the disruption, with a knock on effect on the system.
The spokesman added: "Thank you for your patience, and we are sorry for any inconvenience."