The National Transportation Safety Board (NTSB) has faulted Norfolk Southern for its decision to set toxic chemicals ablaze after the derailment of a train in East Palestine, Ohio, in February 2023.

In its findings from its investigation, released on June 25, the NTSB blamed an overheated, defective wheel bearing for a crash that derailed 38 total cars in February of 2023, 11 of which were carrying hazardous materials. Investigators also criticized the decision to conduct a "vent and burn" exercise to release and incinerate the dangerous chemicals at the site of the derailment. At the time, Norfolk Southern believed that the derailed cars carrying the materials were at risk of exploding, a conclusion the NTSB said was "based on incomplete and misleading information."

"A vent and burn procedure should be a last resort, used when a tank car is about to fail," the NTSB said, describing how the process "resulted in a mushroom cloud that towered over the town and surrounding area." 

Although overheated wheel bearings are described by the NTSB as a "common cause" for train accidents, the train in this instance didn't pass by a "hot bearing detector" — which warns crews to stop trains before a derailment occurs — until the bearing was about to cause its axle to fail.

"The difficulty of accurately measuring temperature inside the bearing, combined with Norfolk Southern’s standard operating procedures and the spacing between detectors, meant the crew did not receive adequate warning to stop the train before the derailment," the NTSB said. 

The NTSB issued a series of safety recommendations as well, pushing for shorter distances between hot bearing detectors, updates to vent and burn policies, and better processes to alert first responders to potentially dangerous chemicals on board trains directly following derailments.