A bullet train running at a speed of 280 kilometers per hour had a door open during part of its journey from Sendai to Tokyo on Wednesday morning, but no passengers were injured, East Japan Railway Co. said.
The incident lasted 40 seconds and at one point the door was wide open.
Such occurrences are rare on Japanese trains, which are known for their safety and punctuality.
The problem was caused by a cleaner who forgot to lock the device that is used to manually open and close the doors, the train operator said.
The conductor of the Hayabusa No. 46 shinkansen made an emergency stop inside a tunnel in Shibata, Miyagi Prefecture, after a warning indicator showed that a door on the ninth train car was open. The train resumed its journey 15 minutes later after the problem was fixed.
The crew did not notice the cleaner's mistake as the door was closed when the train left Sendai at 10:15 a.m.
Around 340 passengers were aboard the train but nobody was standing near the door.
The bullet train arrived at its final destination 19 minutes late. The problem delayed seven trains for up to 28 minutes, affecting around 3,300 passengers.
The transport ministry urged JR East to prevent a similar incident.
