The two key crew members who could reveal what happened in a fatal Amtrak derailment remain hospitalized in Washington state and have not yet been interviewed by federal investigators.

One of the two men, who have not been identified, was a trainee familiarizing himself with the route and locomotive operations when the train barreled at 80 mph into a curve with a posted speed limit of 30 mph. It also was the inaugural run for the train on tracks that had just been refurbished by the regional transit authority, which owns them.

National Transportation Safety Board investigators said that emergency brakes appeared to have been triggered automatically — and not by the engineer — as the train careered into a sharp left-hand curve.

Three people were killed and more than 100 were taken to hospitals after one of two engines and several cars of the 12-car train bound from Seattle to Portland, Ore., toppled from a bridge onto Interstate 5 below. Two of the victims — Zack Willhoite and Jim Hamre — were described as close friends and train buffs. The Pierce County medical examiner's office on Wednesday identified the third person as Benjamin Gran, 40, of Auburn, Wash.

Peter Knudson of the NTSB said investigators were eager to interview the two men in the lead locomotive.

"A big question will be what we hear when we talk to the front-end crew," he said.

He said it was uncertain when the two crew members would be available to be interviewed.

In a similar 2015 Amtrak crash that killed eight passengers in Philadelphia, the NTSB determined that the engineer was distracted by a radio report of a rock being thrown at another train and thought he already had passed a major curve that actually lay ahead of his train.

Knudson stressed that in the Washington-state train wreck, whether the engineer was distracted by conversation with the trainee was one of many questions that will be asked before federal investigators reach a conclusion.

Investigators also will look at whether the transit agency, Sound Transit, rushed to finish rebuilding what is known as the Point Defiance Bypass to receive federal stimulus funding that was due to expire.

Before the stimulus money became available, the $181 million bypass rebuild was projected for completion in 2019, but the project was accelerated after the state received $800 million in stimulus money to improve rail service between Portland and Vancouver, B.C.

Sound Transit entered into a 2016 agreement that stipulated: "This project is under a very aggressive schedule, and . . . a one-month delay would create a significant impact to the project schedule. Under the terms and conditions of the funding, all construction must be completed by June 30, 2017."

A key goal, according to the agreement, was to "reduce travel time between Portland and Seattle." The bypass, which saved the railroad 10 to 20 minutes by avoiding a more scenic but slower passage along the coastline, was finished in the spring.

One thing that had not been finished was the installation of an automatic braking system called positive train control (PTC), which investigators said would have slowed the train as it entered the curve.

In January, an official overseeing the project said "PTC will go in the forthcoming months, before we start service."

But Congress postponed until 2018 a mandate that all railroads adopt the system. Sound Transit took advantage of that, planning to install speed sensors on the track bed next year.

"None of us want to ever appear at a site like this," said Amtrak President Richard Anderson. "We share everyone's sense of urgency to identify exactly what caused this event and are cooperating fully with the investigation, led by the NTSB. Amtrak will do the right thing, based on whatever the findings indicate."