"Contributing to the derailment was CSX Transportation's failure to weld the rail and, thereby, remove the temporary joint before the accident," the report reads.

The investigation is now officially closed.

The 31-car CSX train was traveling at 48 mph when it derailed, under the posted speed limit. The cars that jumped the track included seven tanker cars carrying ethanol, one carrying phthalic anhydride and one carrying liquefied petroleum gas. The cars carrying ethanol and those near them caught fire and about 1,500 residents in surrounding homes had to be evacuated and about 400 had to be out of their homes for several days.

The estimated damages topped $8.48 million, according to the NTSB report, and that included the environmental cleanup.

CSXT agreed to pay $607,599 for local out-of-pocket costs incurred by communities, fire departments and first-responders.