Three years after a pipeline exploded near Danville, leaving one person dead, federal regulators have released their final report on what caused it.The pipeline exploded in August of 2019, killing one, injuring six, and displacing 75 people from their homes, according to the report.The National Transportation Safety Board released its final report saying that one of the causes was a manufacturing defect in the pipeline.A statement from the report said:"​​​The probable cause of the Aug. 1, 2019, Enbridge Inc. pipeline rupture and resulting fire was the combination of a pre-existing hard spot (a manufacturing defect), degraded coating, and ineffective cathodic protection applied following a 2014 gas flow reversal project, which resulted in hydrogen induced cracking at the outer surface of Line 15 and the subsequent failure of the pipeline."Contributing to the accident was the 2014 gas flow reversal project that increased external corrosion and hydrogen evolution. Also contributing to this accident was Enbridge’s integrity management program, which did not accurately assess the integrity of the pipeline or estimate the risk from interacting threats."Watch our coverage of the explosion below:In total, five residences were destroyed by fires caused by the explosion and another 14 were damaged. Fires from the explosion lasted several hours before crews were able to put them out.The pipeline, which is owned and operated by Enbridge, stretched more than 9,000 miles from the Mexican border to New York City.Enbridge released a statement saying it was deeply sorry and has worked diligently to improve the safety of its pipelines.