Initial investigation into a train derailment in southern Colorado suggests the accident was caused by a broken rail, officials said Tuesday.
The derailment, which took place on Sunday, sent 30 cars from a BNSF coal train off the tracks, collapsing a bridge over Interstate 25 and killing one person who was driving a semi trailer on the road.
A nine-mile-long stretch of I-25, between Colorado Springs and Pueblo, will remain closed for days while crews clean up spilled coal and other debris. Authorities will need to investigate whether the spilled cargo damaged the roadway.
Traffic that would normally travel on I-25 is being routed through Penrose, Colorado.
Federal investigators will now try to determine what broke the rail, and why train crews didn't receive warnings about the damage.
Train derailment closes Colorado interstate
A train derailment near Pueblo, Colorado, has shut down both directions of an interstate, leaving behind dozens of mangled train cars.
It wasn't known Tuesday whether the affected track had a system in place to monitor stress on track rails. Such systems can provide early warning before an accident occurs, and can stop approaching trains in the event of a track failure.
BNSF had not responded to questions from The Associated Press on the matter as of Tuesday.
NTSB spokesperson Sarah Taylor Sulick told the outlet investigators would determine if the track was equipped with that system as part of their inquiry.
"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.