Operations resumed on Tokyo’s Yamanote Line around 9 a.m. Monday after trains on the capital's major commuter artery were halted for hours.
Ahead of the reopening, JR East said fewer trains than usual would be operating.
The railway said the suspension had been due to the failure of a signal system at Osaki Station, with crews attempting to fix the problem encountering difficulties before resolving the issues.
The line’s inner and outer loops had both been offline from the scheduled first trains following the malfunction of the signal equipment, which was discovered at about 2:30 a.m., NHK reported.
The railway operator had earlier said operations would resume by noon, but in a later update it said restoration work had progressed more quickly than expected.