Two damaged train cars sit on flatbed trailers after being taken from the scene of an Amtrak train crash in DuPont, Washington, Dec. 19, 2017.
Two damaged train cars sit on flatbed trailers after being taken from the scene of an Amtrak train crash in DuPont, Washington, Dec. 19, 2017.

As they probe a deadly train derailment in the northwestern U.S. state of Washington, federal investigators say they hope crew members will be able to give information in the coming days that will help explain Monday's accident.

The train went off the tracks on a curve south of Seattle traveling 129 kilometers per hour in an area where the speed limit was 48 kilometers per hour.

National Transportation Safety Board member Bella Dinh-Zarr told reporters Tuesday that the train's emergency brakes were automatically activated, rather than being initiated by the engineer, when the accident took place.

She also said that in addition to the engineer, there was also a conductor inside the cab who was "getting experience and familiarizing himself with the territory."

There were about 80 passengers and six crew members on board the train. The derailment sent some of the train cars onto a highway below. Three passengers were killed and more than 70 were injured.

Cars from an Amtrak train that derailed above lie
Cars from an Amtrak train that derailed above lie spilled onto Interstate 5, Dec. 18, 2017, in DuPont, Wash.

?Dinh-Zarr said all of the crew members were hospitalized and that investigators were scheduling interviews with them once they are medically cleared.

The train was operating on a new route along refurbished freight tracks meant to give passengers a faster trip through the region.

Dinh-Zarr said testing of the new route began in January and that Amtrak crews had been operating trains without passengers on the tracks for at least two weeks before the derailment.

The NTSB has examined a data recorder from the train's rear locomotive and will be comparing those results to a recorder investigators obtained from the front locomotive on Tuesday. The agency also has inward- and outward-facing cameras from the train, but Dinh-Zarr said those were damaged in the derailment and had been sent to the agency's headquarters in Washington, D.C., to be evaluated.

Dinh-Zarr also said it is standard protocol to look at the possibility crew members were distracted, including examining their cell phone records, as well as a number of other potential factors that could play a role in an accident.

"We look at it from the beginning of the run all the way to the end of the run, and to see as the crew makes changes, as the engineer makes decisions, how that influenced the activity," she said.

Cars from an Amtrak train lay spilled onto Interst
Cars from an Amtrak train lay spilled onto Interstate 5 below alongside smashed vehicles as some train cars remain on the tracks above, Dec. 18, 2017, in DuPont, Wash.

The stretch of track where the derailment took place does not yet have a system known as positive train control, which can take control of a train and either slow it down or make it come to a stop if it exceeds speed limits.

Local officials said the system was due to be operational in the area by the middle of 2018.

That would beat a deadline ordered by Congress that came after a series of earlier train accidents. Congress originally mandated railroads have positive train control in place by the end of 2015, but rail companies won a delay that pushed the deadline to the end of 2018.

Amtrak President and CEO Richard Anderson said Tuesday it makes "scientific sense" to utilize the technology.

"We are hug supporters of positive train control. We have all of our capital allocated to get it done," he said. "There's no one that wants positive train control more than Amtrak."

This photo provided by Washington State Patrol sho
This photo provided by Washington State Patrol shows an Amtrak train that derailed south of Seattle on Dec. 18, 2017.

In May 2015, an Amtrak train derailed in Philadelphia as it went into a curve at more than double the posted speed limit. Eight people died in that accident, which investigators blamed on the engineer being distracted by radio conversations between trains and dispatchers about trains being hit by rocks.

The site of the Philadelphia derailment was not equipped with positive train control technology, and the NTSB determined the accident could have been prevented if that system or another form of control had been in place to force the train to follow the speed limit.