DUPONT, Wash. — Federal investigators in the deadly Amtrak wreck want to know whether the engineer was distracted by a second person in his cab as his train hurtled into a curve at more than twice the speed limit.

Three people were killed Monday when the train barreled into a 30 mph zone at 80 mph and plunged off an overpass, sending rail cars plummeting onto a busy interstate highway south of Seattle.

A locomotive from the train was removed Wednesday morning from the scene. The wreck closed the southbound lanes of Interstate 5 south of Tacoma, during the busy holiday travel period. Authorities said they’d reopen the freeway lanes as soon as possible.

A conductor in training was in the locomotive with the engineer at the time, investigators said. A federal official who was not authorized to discuss the matter publicly and spoke on condition of anonymity said authorities want to know whether the engineer lost “situational awareness” — didn’t realize where he was — because of that.