Investigators expect to finish interviewing the engineer of a derailed New York City commuter train on Wednesday.

National Transportation Safety Board spokesman Keith Holloway said Tuesday that investigators began talking to engineer William Rockefeller on Monday. But they postponed completing the interview.

Holloway wouldn’t say why.

Union leader Anthony Bottalico says it’s because Rockefeller hadn’t slept in almost 24 hours and was “very distraught.”

Bottalico is the general chairman of the Association of Commuter Rail Employees.

He and Holloway both say Rockefeller’s session with investigators is likely to resume Wednesday.

A lawyer representing Rockefeller didn’t immediately return a call Tuesday.

Four people died and more than 60 were injured in the Metro-North Railroad train wreck Sunday. The NTSB says the train was going 82 mph around a 30-mph curve.

(AP)