JR Keihin Tohoku Line trains were halted for about four hours Monday morning after a train hit a power shovel scoop apparently left on the tracks after repair work.
Although no one was injured, the accident affected some 132,000 people during the morning rush hour, officials at East Japan Railway Co. said.
The train schedule was disrupted for most of the morning.
According to JR East, workers employed by an affiliate started the maintenance work after the last night train had passed, finishing at around 4 a.m.
But the scoop, measuring some 85 cm × 65 cm × 105 cm, was left between the rails in Shinagawa Ward.
The shovel was struck by the first northbound train of the day. Operations between Higashi-Jujo and Kamata stations were suspended until 8:45 a.m., while some trains on the Tokaido Line, which runs parallel to the Keihin Tohoku Line, were also temporarily halted.
JR East said it was unclear whether the scoop had fallen off the construction machinery or whether workers had forgotten to clear it away after removing it from the power shovel.
Officials admitted, however, that no one noticed the scoop on the tracks even during the final inspection of the working area before the workers left the site.
Hiroshi Okawa, head of JR East's Tokyo office, voiced deep regret over the incident.
