Poor track conditions that should have been flagged by a freight railroad company’s inspectors caused the derailment of an Amtrak train in Montana that killed three people and injured 49 others in 2021, federal investigators said Thursday in a final report.

The severity of the injuries were made worse by the Amtrak train’s lack of seatbelts and windows that weren’t strong enough to keep passengers from being ejected when the train derailed, the National Transportation Safety Board found.

Amtrak’s Empire Builder derailed Sept. 25, 2021, in northern Montana while en route from Chicago to Seattle and Portland, Oregon, with 165 people on board, including its crew.

FREIGHT TRAIN THAT DERAILED INTO YELLOWSTONE RIVER AS BRIDGE COLLAPSED WAS HAULING HOT ASPHALT, MOLTEN SULFUR

Six people were ejected from the train's observation car, which has larger windows and was one of three cars that ended up on its side. One person who had been riding in the observation car died, as did two people who were in the vestibule between the observation car and the car behind it, the NTSB said.

The combination of wear and damage to the railroad track, had it been noticed by BNSF Railway inspectors, should have led to the track being replaced before the derailment occurred, the report found. Investigators also found that a train inspector’s workload likely prevented him from doing a walking inspection of the area before the derailment.

The poor track conditions included a worn rail, vertical track deflection, misalignment and instability in the rail bed, the report found. The track is owned by BNSF railroad. The NTSB said BNSF’s lack of action indicated "a shortcoming in its safety culture."

"This tragedy is a powerful reminder that there’s no substitute for robust track inspection practices, which can prevent derailments by identifying track conditions that may deteriorate over time," said NTSB Chair Jennifer Homendy.

Emails sent to Amtrak spokesperson Marc Magliari and BNSF railroad spokesperson Lena Kent were not immediately returned.

Montana Amtrak derailment site

Workers are seen at the site of an Amtrak passenger train derailment near Joplin, Montana, Sept. 27, 2021. (AP Photo/Ted S. Warren, File)

Kristofer Riddle, an attorney for four passengers who were on the train when it derailed, said he was unsurprised by the report’s findings because damaged tracks are well-known safety concerns.

What continues to outrage him, he said, is that the same safety concerns arise after passenger train accidents without any changes. One of his clients, Justin Ruddell, was in a train car restroom when it derailed near the small town of Joplin, whipping the door open and pouring dirt and gravel atop him as he clung for dear life.

"The thing here that’s particularly egregious is this is the story that you hear after derailments time and time again," Riddle said.

Investigators also found that if a locomotive equipped with an automated vehicle-track interaction monitoring system had traveled over the area, it would have detected the deteriorating track conditions and BSNF Railway would have had an opportunity to make repairs. NTSB is recommending that all trains be equipped with that technology.

Thursday's finding follows what was revealed earlier this year in the agency’s investigative documents. Investigators identified a deteriorating track based on video footage, including from two BNSF freight trains that went around the accident curve within 90 minutes before the Amtrak derailment.

The problem got worse as the freight trains traveled over the area before the crash.

Killed in the accident were Margie and Don Vardahoe, a Georgia couple on a cross-country trip to mark their 50th wedding anniversary, and Zachariah Schneider, 28, a software developer from Illinois.

CALIFORNIA AMTRAK TRAIN DERAILS AFTER COLLIDING WITH WATER TRUCK, NO ONE SERIOUSLY INJURED

Families of those who were killed and injured passengers have filed lawsuits against BSNF railroad and against Amtrak.

BNSF is owned by Warren Buffett’s Omaha, Nebraska-based Berkshire Hathaway conglomerate.

Railroad unions have expressed concerns that the lean operating model all the major freight railroads have adopted has made railroads riskier because employees are spread so thin and some workers have to take care of such large territories that it's hard to keep up with preventative maintenance.

The railroads have defended their practices and don’t believe they have sacrificed safety when they streamlined operations.

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Railroad safety has become a hot topic this year in the wake of a fiery Ohio derailment in February and several other crashes that prompted regulators and members of Congress to propose a series of reforms.