SEATTLE -- An Amtrak train that derailed as it was making the first trip for paying passengers over upgraded tracks may have been going much faster than the speed limit.
Train 501 was going more than 80 mph about one-quarter mile before it entered a curve where the speed limit was much lower, according to rail analysts transitdocs.com, a website that maps Amtrak train locations and speeds using data from the railroad's train tracker app.
A track chart prepared by the Washington State Department of Transportation shows the maximum speed drops from 79 mph to 30 mph for passenger trains just before the tracks curve to cross Interstate 5.
The chart, dated Feb. 7, 2017, was submitted to the Federal Railroad Administration in anticipation of the start of passenger service along a new bypass route that shaves 10 minutes off the trip between Seattle and Portland.
Another Sound Transit spokeswoman, Rachelle Cunningham, confirmed the maximum allowable speed was 30 mph at the derailment point, but could not say where that lower limit began.
It wasn't clear how fast the train was moving at the moment it derailed.
Chris Karnes, a passenger on the train, said the train was moving at a "pretty good pace" -- roughly 70 to 80 mph, judging from the fact the train was passing cars on the highway -- when it derailed.
Karnes is chairman of the Pierce Transit Community Transportation Advisory Group. He said he boarded the train between Seattle and Tacoma and took a seat on the third or fourth car.
Karnes' car derailed -- only the rear locomotive remained on the tracks -- and passengers kicked out a window and climbed down an embankment to summon help, he said.
He did not know what caused the derailment, but said the train had previously taken tighter curves at the same pace without any issues.
Another passenger Scott Claggett said, "I was going around the curve. We started to tilt and you're just like, we're going way too fast to be tilting like this. The car tilted, everything started flying toward me. People started flying toward me. There was glass, smoke."
The tracks, known as the Point Defiance Bypass, are owned by Sound Transit, a transit agency serving Western Washington. They were previously owned by BNSF and were used for occasional freight and military transport.
Thirteen train cars jumped the tracks on Monday, killing at least three people on board and hitting several vehicles on Interstate 5 below. The Pierce County Sheriff's Office said several vehicles on Interstate 5 were struck by falling train cars and multiple motorists were injured.
While the cause of the crash was not known, even people who opposed the new route on safety grounds said the derailment surprised them.
An official briefed on the investigation told The Associated Press that preliminary signs indicate Train 501 may have struck something before going off the track about 40 miles south of Tacoma.
The train was traveling a faster route Monday that had been used occasionally by freight trains until a $181 million upgrade opened it to passenger travel.
Track testing began in January and February in advance of Monday's launch and continued through at least July, according to the Washington State Department of Transportation.
The mayor of Lakewood, which is situated along the new route, predicted a deadly crash — but one involving a fast-moving train hitting a car or pedestrian at a grade-crossing, not a train tumbling off an overpass. At a recent public meeting, he called on state planners to build overpass-like rail structures instead of having trains cross busy streets.
The Associated Press and CNN contributed to this article.