DENVER (AP) — A truck driver was killed when a train derailed near Pueblo and caused a railroad bridge to collapse onto a major highway — crushing the semitruck, spilling coal and mangled rail cars across the roadway and shutting down traffic indefinitely, authorities said Monday.

The 60-year-old driver was initially said to be trapped in the Sunday afternoon accident on Interstate 25, but authorities said Monday that he had died.

The partially collapsed bridge could be seen Monday afternoon with the semitruck caught beneath it in the northbound right lane. Derailed train cars were piled up on the bridge and along the tracks to the northeast and large amounts of coal covered a portion of the highway.

A nine-mile (14-kilometer) stretch of I-25 — the main north-south road corridor in Colorado, used by 39,000 to 44,000 vehicles daily — was shut down in what the Colorado Department of Transportation said Monday would be an extended closure.

The bridge partially collapsed when the train hauling 124 cars of coal derailed at about 3:30 p.m. Sunday just as the semitrailer truck passed beneath it, the National Transportation Safety Board said.

Thirty cars derailed, the agency said.

Colorado train derailment: NTSB arrives

Investigators from the NTSB arrived Monday at the site, just north of Pueblo and about 114 miles (183 kilometers) south of Denver. They will determine the cause after looking at the adequacy of prior track inspections, the condition and maintenance history of the bridge and any issues with the train or rail cars, the agency said in a statement. A preliminary report will be released in 30 days.

It was not immediately known whether any other vehicles were involved, Pueblo County Sheriff’s Office spokesperson Gayle Perez said.

It could take as long as 48 hours to clear the coal and other debris and make the highway passable, Gov. Jared Polis said. That work won’t begin until federal investigators give the state clearance to proceed, Polis said. He added that Colorado had been waiting months to receive federal money already dedicated for safety and rail projects.

“Those improvements come too late to prevent this incident,” the Democratic governor said in a statement. “I am saddened that a life was lost in this train derailment and send my condolences to his family and loved ones.”

What may have caused the train derailment?

The bridge was built in 1958, Colorado Transportation Department spokesperson Bob Wilson said.

Former NTSB accident investigator Russell Quimby said the most likely scenario was that the derailed cars slammed into the side of the bridge, causing the girders that support it to be displaced and causing the bridge to fall. Potential sabotage or vandalism also will be looked at by investigators, he said.

“Usually that’s pretty obvious,” Quimby said. “If they find something that looks like some kind of vandalism or foul play, they would call in the FBI and it would become a crime scene.”

There was some confusion over who owned the bridge. A BNSF spokesperson said it was owned by the state.

Wilson said early Monday that it was BNSF’s bridge and the railroad was responsible for inspecting it. But Wilson later said the ownership was unclear.

Officials didn’t provide details about the truck driver’s death, citing the ongoing investigation.

There were no reported injuries to BNSF crew, according to Kendall Kirkham Sloan, a spokesperson for the Fort Worth, Texas-based freight railroad. BNSF personnel were working with responding agencies to clear the incident as safely as possible, Kirkham Sloan said.

Transportation Secretary Pete Buttigieg said on social media that he had been in touch with Polis and had been briefed by the Federal Railroad and Federal Highway administrations, which were ready to help support a swift return to normal use for the highway and rail routes.

Railroads responsible for maintaining bridges

Unlike highway bridges, government agencies don’t catalog rail bridges and it’s largely up to the railroads to inspect and maintain the ones that they own. Federal officials monitor the inspection programs through audits but there is no inventory on the condition of the bridges.

There are somewhere between 61,000 and more than 100,000 railroad bridges across the U.S., according to figures provided by the Federal Railway Administration. The agency defines bridges as having a span of 20 feet or more, whereas some railroads count even short crossings over culverts as bridges.

Congress established the parameters of the government’s oversight of bridges and railway administration officials have previously said they were not able to alter that approach unilaterally.

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 (226.7 metric tons) of hot asphalt. The collapse, which remains under investigation, involved a steel truss bridge.

That’s different than the type of bridge that Colorado officials said collapsed on Sunday. The bridge near Pueblo was a 188-foot-long steel girder bridge, said Wilson. It was 14 feet (4 meters) feet wide with a clearance of 16.3 feet (5 meters), he said.

Rail bridge collapse ‘extremely’ unusual

Despite the two recent accidents, Quimby said it’s “extremely” unusual for rail bridges to collapse. Quimby said bridges are key pieces of railroad networks and companies have a vested interest in properly maintaining them. Some railroad bridges are more than a century old but still in good repair, he said.

“The railroads take much better care of their bridges than our government does of our road and highway bridges,” he said. “If you have a bridge out, that’s a major problem.”

At least 111 railroad accidents have been caused by bridge failures or bridge misalignments since 1976, according to an Associated Press review of federal accident records. That’s just over two accidents annually on average.

Combined, those derailments caused about $40 million in damages, the records show. That figure does not include the June derailment. Only one of the accidents involved a fatality, when one person was killed and dozens of people injured after an Amtrak train derailed in Arizona in 1997 while crossing a bridge damaged by runoff from heavy rain.

President Joe Biden had been scheduled to visit CS Wind, the world’s largest facility for wind tower manufacturing, in Pueblo on Monday, but postponed the trip to focus on the growing conflict in the Middle East. The White House said a few hours before Biden was set to take off that the trip would be rescheduled.

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Associated Press writers Sarah Brumfield in Washington, D.C. and Josh Funk in Omaha, Nebraska and AP photographer David Zalubowski contributed to this story. Brown contributed from Billings.