"We have ruled out nothing. We are looking at everything," George Black, a member of the National Transportation Safety Board, told CBS News late Wednesday. He predicted it would be months before the cause is pinpointed.
Amtrak's Southwest Chief lies mangled in a cornfield after sixteen of its cars derailed. Melissa Brunner of CBS Affiliate WIBW reports, two sleeper cars were among the six passenger cars that flipped over.
There were no fatalities among the 155 passengers and 15 crewmembers on the Chicago-to-Los Angeles train, but 29 passengers were injured. Fifty-three-year-old Kathy Lambert of Stroh, Indiana, remains hospitalized in critical condition. The mother of three grown daughters underwent surgery to remove an injured spleen and also suffered from a cracked shoulder and bruised ribs, said Marilynn Quick, superintendent of Prairie Heights School Corp. in Angola, where Lambert has worked for 23 years. The other passengers were treated at Topeka hospitals and released.
Passengers and Amtrak officials said the train had just rounded a turn and was going up a slight incline at 60 miles per hour when a loud noise broke the calm. The train began to shake, and cars began tipping over.
"At first I was really scared because I didn't know what would happen but once I got out I was more calm," said Jonathan Kimmerer, who was traveling with his wife Jackie.
"We were just lucky all of us came out okay, then we figured how to get the window open and then we just started shoving people through the window," she added.
"I thought I was all through," said passenger Jeanne Walker, who was awakened by the noise and the sense that the car was falling onto its right side. "I kept thinking, 'This is it, this is it.' "
Fellow rider Raven Freeman heard "a loud noise Â— two or three pops Â— and the train just started shaking from side to side. I didn't know what was going to happen next. It was a pretty scary experience."
Rescue crews were quickly on the scene, but officials say it took about four hours to free all the passengers from the train. "The (Amtrak crewmembers) were very helpful, they didn't panic, they took everything under control, it was pretty good," said passenger Miguel Cuevas.
Officials from Amtrak, the Federal Railroad Administration and Burlington Northern Santa Fe Railway are aiding the crash probe.
The NTSB said a preliminary investigation revealed two fractured rails on the track, but investigators were not sure whether they were responsible for the derailment.
The track had passed a visual inspection Tuesday and was electronically inspected last fall.
Steve Forsberg, a spokesman for Burlington Northern Santa Fe, said derailments generaly could be blamed on human error, a mechanical defect of the train or a defect along the track. "It's unclear what caused it," he said.
Amtrak serves about 21 million passengers a year. In 1997, 245 Amtrak trains were involved in accidents reportable to the Federal Railroad Administration, according to Amtrak statistics. They caused 1,020 crew injuries and 266 passenger injuries, most of them minor.
Relatives of passengers may call a special Amtrak hotline for information: 800-523-9101.