Transformer fire near Tamachi halts Yamanote and Keihin-Tohoku lines

A power outage tied to overnight maintenance and a subsequent transformer fire near Tamachi Station paralyzed two of Tokyo's busiest commuter routes on the morning of January 16, forcing mass evacuations and snarling the morning rush for hundreds of thousands of passengers.

Rail operator East Japan Railway Co. cut power overnight to a supply facility serving the section of track between Shimbashi and Shinagawa for infrastructure work, and staff were unable to restore the supply before the first scheduled trains. The outage first occurred at about 3:50 a.m., and just before 8:00 a.m. flames were reported at a transformer in the track area near Tamachi, which is served by both the Yamanote and Keihin-Tohoku lines. Authorities have not confirmed whether the earlier power disruption and the transformer blaze were directly linked; investigations have been ordered.

JR East halted services on the Yamanote Line and the Keihin-Tohoku Line in all directions, leaving commuters stranded on platforms and aboard trains. Footage showed passengers disembarking from a Keihin-Tohoku train stuck between stations and walking along tracks to the nearest stations under the assistance of firefighters, police and railway staff. Some evacuations involved passengers walking from trains stranded between Shimbashi and Hamamatsu stations.

Accounts differed on how quickly the fire was brought under control. Some operational reports said the blaze was mostly extinguished in about 30 minutes, while other emergency responses logged a timeline closer to 90 minutes before full control. Both timeframes were recorded as the fire department and police continued on-site operations and a formal inquiry.

The shutdown of the Yamanote Line, a vital loop serving major hubs including Shinjuku, Tokyo and Ueno that handles millions of journeys daily, had an immediate ripple effect through the city's transport network. Major transfer stations filled rapidly, subway lines and bus services were overloaded, and alternative modes such as bicycle sharing saw sudden spikes in demand. JR East estimated that roughly 670,000 passengers were affected by the outage. The stop in services was characterized by some observers as lasting about eight hours; JR East subsequently restored full Yamanote operations early in the afternoon and Keihin-Tohoku services resumed in the same time frame.

Emergency services reported that five people were treated after falling ill during the incident. There were no detailed reports of serious injuries. Firefighters, police and railway crews coordinated evacuations and crowd control, and staff worked through the afternoon to normalize service and inspect electrical systems.

Transport Minister Yasushi Kaneko ordered JR East to investigate the cause of the incident and to implement measures to prevent recurrence, signaling potential regulatory scrutiny of maintenance practices and safety protocols. The incident underscores the vulnerability of dense urban transit systems to cascading failures when electrical infrastructure intersects with heavy commuter demand.

Beyond the immediate disruption to individual commuters, the stoppage highlighted broader concerns about resilience in one of the world's busiest urban transport systems. Tokyo's role as a global financial and cultural hub means such interruptions have local and international implications, stretching supply chains, affecting international travellers and testing public confidence in critical infrastructure. Authorities have pledged full investigations into the sequence of events and to publish findings that explain the relation, if any, between the overnight power cut and the transformer fire.