(Bloomberg) -- The Amtrak train derailment that killed three people Saturday in Montana occurred at a split in the rail lines, suggesting some kind of failure at that point may have led it to jump the tracks, a safety expert said. 

The rear cars on the westbound Empire Builder, which was headed to Seattle and Portland from Chicago, came off the tracks at the so-called switch, some of them rolling on their sides, according to photos of the scene. 

“It looks like the first third of the train negotiated the switch successfully and then all heck broke loose,” said Grady Cothen, a retired deputy associate administrator for safety standards at the Federal Railroad Administration. 

While it’s too soon to say for certain whether the switch played a role in the accident, it will be a focus of investigators from the National Transportation Safety Board, the FRA and others on the scene, said Cothen, who isn’t involved in the investigation of the Montana derailment. 

Three people died and five were hospitalized in the accident Saturday afternoon, Montana Governor Greg Gianforte said in a briefing. The train was near the town of Chester in the northern prairie lands near Canada. Dozens more of the 141 passengers and 17 crew suffered minor injuries. 

There could be multiple reasons why a train might derail at a switch, Cothen said. They include such things as a malfunctioning switch or an equipment problem on the train, he said. 

Some type of unrelated failure, such as a damaged section of track that just happened to occur near the switch, was also possible, he said. 

Berkshire Hathaway Inc.’s BNSF freight railroad owns the line where the accident occurred. Track switches are typically used to create a parallel rail line for a short distance so that trains going in opposite directions can pass each other. 

BNSF had installed a safety system known as positive train control on that section of track that automatically ensures trains won’t go too fast or collide with other trains, the company said on its website. 

Amtrak and BNSF didn’t immediately respond to requests for comment. NTSB typically prohibits parties in an investigation from commenting during a probe.

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