2023 Ohio train accident
About 48 hours later, the NTSB released a first report that stated  that the derailment was caused by a mechanical problem on one of the railcars' trucks.   This may be connected to reports that an axle was observed throwing sparks about an hour before. The crew received an alarm from a wayside defect detector shortly before the derailment indicating a mechanical problem, and then an emergency brake application initiated.