A broken rail caused a train derailment that collapsed a bridge over an interstate highway in Colorado, killing a truck driver and blocking the road for days, federal authorities said Tuesday, based on their preliminary investigation.

Officials will investigate how the rail broke and why warning systems did not alert crews to the condition of the track, the National Transportation Safety Board said. An agency spokesperson said officials had no reason to believe sabotage caused the derailment.

The steel bridge, built in 1958, collapsed Sunday when 30 cars from a BNSF Railway train hauling coal derailed while crossing over Interstate 25 north of Pueblo.

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The driver of a semitrailer truck passing beneath the bridge was killed. I-25, the main north-south route through Colorado, is expected to remain closed for several more days as crews clear away coal and other debris.

Broken rails and other track problems are a leading cause of derailments, according to federal accident data.

The NTSB has long recommended that railroads install more automatic monitoring systems that can detect problems with tracks early on and prevent accidents. The agency repeated its call for those systems in July in response to a fatal Amtrak derailment along BNSF-owned tracks in northern Montana two years ago.

It was not immediately known whether the track where Sunday’s derailment occurred had such a system. NTSB spokesperson Sarah Taylor Sulick said that was part of the investigation.

“They will be pulling maintenance records. They’ll be interviewing people involved. They’ll be talking to the railroad. They’ll be talking to the state,” Sulick said.

Representatives of BNSF did not immediately respond to emailed questions.

The site of a deadly train derailment is seen on Monday, Oct. 16, 2023, near Pueblo, Colorado. (AP Photo/David Zalubowski)

Former NTSB investigator Russell Quimby said an automatic warning system likely was in place in Colorado because the accident happened along one of BNSF’s main routes between Denver and Texas, where the railroad is headquartered and which has numerous coal-burning power plants.

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Those systems are integrated into the track and built so that if a rail breaks, they would stop any approaching trains, Quimby said. However, if the rail broke as the train was traveling over it, there would be little the engineer on board could do, since it can take over a mile to stop a fully loaded freight train, he said.

“The most stress you’re going to have on that rail is when something’s sitting on it. A fully loaded rail car, it’s putting over 15 tons of pressure on the track per wheel,” he said.

Railroads regularly inspect their tracks, looking for cracks or other defects in the rails that could make them more susceptible to breaking. Repairs are scheduled based on the severity of the defect, so even if a problem had been identified, it might not have been fixed immediately.

BNSF has not said when it last conducted an inspection or responded to requests to view its inspection records.

A nine-mile stretch of I-25 — used by 39,000 to 44,000 vehicles daily — was shut down. Traffic was being detoured around the derailment site and through the town of Penrose, almost 30 miles west of Pueblo.

Hundreds of tons of coal and mangled railcars that landed on I-25 were expected to be cleared from the road by Wednesday afternoon, officials said. After that, officials will be able to assess how badly the road is damaged and what repairs are needed.

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The truck driver killed was Lafollette Henderson, 60, of Compton, California, said Pueblo County Coroner Brian Cotter.

Pressure for the railroad industry to improve safety has grown since a February derailment of a train hauling toxic chemicals that triggered evacuations in Ohio and Pennsylvania. There were more than 12,400 train derailments in the U.S. in the past decade, or more than 1,200 annually, according to Federal Railroad Administration data based on reports submitted by railroads.

Since 1976, at least 111 railroad accidents have been caused by bridge failures or bridge misalignments since 1976, according to an Associated Press review of derailment reports submitted by railroads to the Federal Railroad Administration. That’s just over two accidents annually on average.

Sunday’s accident follows a railroad bridge collapse in June along a Montana Rail Link route in southern Montana that sent railcars with oil products plunging into the Yellowstone River, spilling molten sulfur and up to 250 tons of hot asphalt. The accident remains under investigation.