"The Metro-North Railroad train that hurtled off the rails on a sleepy holiday weekend morning was traveling 82 miles per hour as it approached one of the sharpest curves in the region’s rail system, federal investigators said on Monday — nearly three times the speed permitted through the turn. The throttle was still engaged — giving the engine power — until six seconds before the locomotive, in the rear of the train, came to a stop around 7:20 a.m. Sunday after the train careered toward the Harlem River, killing four people and injuring more than 70, north of Spuyten Duyvil station in the Bronx, officials said. Asked if the safety board was looking into the possibility that the engineer, William Rockefeller, fell asleep, was using his cellphone or was otherwise distracted, a spokesman for the board, Keith Holloway, said, “Part of our investigation, as in all investigations, is to look at human performance factors.” Mr. Rockefeller’s cellphone was recovered as “part of our routine process,” Mr. Weener said, and the results of drug and alcohol tests conducted after the crash were not yet known. Mr. Rockefeller was treated at a hospital and released. The authorities said that the train’s brakes appeared to have been operating effectively shortly before the crash.