A door opened when the bullet train was running at a speed of 280 kph on the Tohoku Shinkansen Line on Aug. 21, forcing the driver to hit the brakes.

No injuries were reported in the incident, which was apparently caused by the cleaning crew forgetting to return the handle that allows the door to be opened manually back to its proper position.

East Japan Railway Co. said the incident delayed seven Shinkansen trains by up to 28 minutes in both inbound and outbound directions, affecting about 3,300 passengers.

The driver was alerted by an alarm at around 10:17 a.m. that a door of Car No. 9 had opened when the Hayabusa No. 46 was running between Sendai Station and Shiroishi-Zao Station, both in Miyagi Prefecture.

The 10-car train, bound for Tokyo, was brought to an emergency stop, and the conductor found that the door had almost fully opened. JR East officials said the door had been open for about 40 seconds.

The red emergency door handle, which allows the door to be opened manually, had been pulled. An emergency door handle, covered with a panel, is set up above each of the doors.

JR East officials checked footage from a security camera and found that a cleaning staff member had pulled the emergency door handle while the train was being cleaned before it left Sendai Station.

The handle’s status was overlooked during the final check ahead of the departure.

Usually, all doors of a Shinkansen train are controlled by the conductor. But the cleaning crew can operate the emergency door handle to manually open a door.

Trains cannot leave a station if any of its doors is open. The door of the Hayabusa No. 46 was closed but not locked, and apparently opened due to vibrations from the speed of the train.

The cover panel for an emergency door handle is locked when the Shinkansen train exceeds 30 kph so that the handle cannot be operated during a run.

The latest E7 series Shinkansen is equipped with a safety system that can detect if the panel is open. But such a system was not installed on the Hayabusa No. 46, which is the E5 series train.

“We will consider installing a safety system similar to that for the E7 series onto the E5 series and other models as soon as possible,” said Yusuke Konishi, director in charge of Shinkansen trains at JR East.