A detailed update has been released on the May 13 incident that derailed a people mover train that travels between the main terminal at Miami International Airport and its rental car center. According to the report, the train went off the track because of a malfunction with the guide-wheel assembly, which keeps the car locked to the rail.

The train was heading eastbound at 11:03 a.m. when the rear car of the train derailed. The car entered the crossover, got off the track and tipped to the right. The car carried 12 passengers, who were evacuated. Only two people suffered minor injuries.

The investigation, led by Mitsubishi and Crystal Movers, determined that the guide-wheel assembly bolts had not been properly “torqued or worked loose,” the report states. Technicians are required to check for torque marks every three days. The train care had gone through maintenance review the day before and was tested throughout the night, just hours before it derailed.

The report sent to Commissioner Dennis C. Moss Tuesday stated that the Operations and Maintenance department will implement stricter policies for maintenance workers, like a step-by-step sign off procedure to make sure the trains are examined and tuned up to code. Workers will take part in refresher training to prevent any other mechanical failures.

Mitsubishi vehicle engineers are studying the damaged car and the guide posts to see how they can efficiently fix them within the next four weeks. The approximate damage is $400,000.