The head of the National Transportation Safety Board said Tuesday that Norfolk Southern repeatedly tried to interfere with the agency’s investigation into the East Palestine derailment and shape its conclusions about the flawed decision to blow open five tank cars and burn the vinyl chloride inside.

The NTSB also confirmed at Tuesday’s hearing that the February 2023 derailment was caused by a wheel bearing that video showed was on fire for more than 20 miles (32.19 kilometers) beforehand but wasn’t caught in time by inaccurate trackside detectors. The board also approved more than two dozen recommendations to prevent similar disasters, including establishing federal rules for those detectors and the way railroads respond to them along with reviewing how officials decide whether to ever conduct a vent and burn again.

More than three dozen freight cars derailed Feb. 3, 2023, on the outskirts of East Palestine near the Pennsylvania border, including 11 carrying hazardous materials. Some residents were evacuated that night, but days later more had to leave their homes amid fears of an imminent explosion. Despite potential health effects, officials intentionally released and burned toxic vinyl chloride three days after the crash, sending flames and smoke into the air.

At the end of the meeting, NTSB Chair Jennifer Homendy accused Norfolk Southern of interfering with the investigation and abusing its status as a party to the probe to help gather information.

“Norfolk Southern’s abuse of the party process was unprecedented and reprehensible,” she said.