YONKERS, N.Y.

- The engineer whose speeding commuter train ran off the rails along a curve, killing four people, nodded at the controls just before the wreck, and by the time he caught himself it was too late, a union official said yesterday.

William Rockefeller "basically nodded," said Anthony Bottalico, leader of the rail employees union, relating what he said the engineer told him.

"He had the equivalent of what we all have when we drive a car. That is, you sometimes have a momentary nod or whatever that might be. How long that lasts, I can't answer that."

Rockefeller's lawyer did not return calls. During a late-afternoon news conference, federal investigators said they were still talking to Rockefeller, and they would not comment on his level of alertness around the time of the Sunday morning wreck in the Bronx.

Separately, however, two law-enforcement officials said the engineer told police at the scene that his mind was wandering before he realized the train was in trouble, and by then it was too late to do anything about it. One of the officials said Rockefeller described himself as being "in a daze" before the wreck.

Questions about Rockefeller's role mounted rapidly after investigators disclosed Monday that the Metro-North Railroad train jumped the tracks after going into a curve at 82 mph, or nearly three times the 30 mph speed limit. In addition to the four people killed, dozens were hurt.

"He caught himself, but he caught himself too late. . . . He powered down, he put the train in emergency, but that was six seconds prior to derailment," Bottalico said.

Rockefeller, who was operating the train from the front car, was treated at a hospital for minor injuries and released.

National Transportation Safety Board member Earl Weener repeated that it was too soon to say whether the accident was caused by human error.