MIAMI (CBSMiami) – A “jumper wire” improperly installed in a people mover train at Miami International Airport caused it to crash into a wall injuring six people nearly three years ago, the National Transportation Safety Board concluded Tuesday.

The agency’s final report stated that the wire, installed by Johnson Controls, Inc. maintenance technicians, prevented the overshoot/overspeed system from activating and stopping the train on November 28, 2008.

“We have seen in this accident and other investigations that too often there is a lack of crucial safeguards,” said NTSB Chairman Deborah A.P. Hersman.

The invesigation determined that Johnson Controls, Inc. failed to properly train it’s technicians regarding the potential disabling of vital train control systems during passenger operations.

They also cited the lack of oversight by the Miami-Dade Aviation Department, the State of Florida and the U.S. Department of Transportation as contributing factors to the accident.