The Tokyo Public Prosecutor’s Office decided Friday not to charge five Tokyo subway employees in connection with a March 2000 derailment and subsequent collision that left five people dead and 64 injured.

The accident was caused by multiple factors, including a weight imbalance in the train wheels on both sides, making it difficult for employees of the Teito Rapid Transit Authority (Eidan) to foresee the accident, prosecutors said.

The prosecutors said they could not pin specific blame on the five Eidan employees, who were in charge of rail maintenance and management at the time.

In March 2001, police turned their case against the five employees over to prosecutors, alleging professional negligence resulting in death and injury, and endangering transportation.

Police alleged the accident occurred because the employees failed to check the condition of the rails and take proper steps to correct a dangerous situation.

But prosecutors have agreed that while there were mistakes in the repair and maintenance of the rails, other factors were also responsible for the accident.

A 77-year-old man from Tokushima Prefecture who lost his 33-year-old son in the accident said there was nothing left for him to do but accept the prosecutors’ decision.

Eidan meanwhile reiterated its apology to the victims and next of kin and vowed such an accident will never happen again. The accident occurred at around 9 a.m. on March 8, 2000, near Naka-Meguro Station on the Hibiya Line, operated by Eidan.

The rear car of a south-bound eight-car train derailed and sideswiped an opposing train on a parallel track. The accident occurred immediately after the south-bound train emerged from a tunnel near the station.

During an inspection by two of the employees in November 1999, according to police, 13 points along the length of rail failed to meet Eidan’s safety standards.

The remaining three overlooked shoddy rail-maintenance work during the following month, in which workers excessively shaved the rails, according to police. The top edges of the rails were supposed to be shaved by 0.2 mm to reduce wheel noise, but up to 1 mm was found to have been shaved off.