A train on a Yokohama subway line derailed Thursday, leading to the line being suspended and delaying passengers, none of whom were injured in the incident.

The first train of the day to run on the Yokohama Municipal Subway Blue Line ran off the tracks at around 5:20 a.m. loal time on Thursday close to Shimoiida station, local police and Yokohama municipal government officials said.

According to police and the train's operator, there were around 130 passengers aboard when the train's six cars derailed.

The cause of the derailment is believed to have been a device left on the tracks by maintenance workers overnight during inspections.

The workers failed to realized they had forgotten the device as a warning light indicated that nothing had been left behind during the maintenance work.

The driver of the train said he felt the impact immediately and quickly applied the emergency brakes, bringing the train to a halt around 40 m from the site of impact.

Passengers aboard were quickly evacuated through the train's emergency exit in the last carriage and walked to Shimoiida Station, the train's operator said.

Trains along the Blue Line were temporarily suspended due to the damaged caused by the derailment and a number of passengers were forced to use the Sotetsu Line from another station to try and finish their commutes to work and school, local police said.

"We are sorry to have caused trouble to many passengers. The incident was likely triggered by human error and we will try to prevent a recurrence," Hirotoshi Shiro, head of Yokohama city's transportation bureau, was quoted as saying.

According to the Yokohama municipal government, this was the first derailment of a passenger service train since the subway line opened in 1972.