The MTA identified the victims Sunday as 54-year-old Donna L. Smith of Newburgh; 58-year-old James G. Lovell of Cold Spring; 59-year-old James M. Ferrari of Montrose; and 35-year-old Ahn Kisook of Queens.
Family members for Smith and Lovell didn't return messages seeking comment Sunday. Relatives for Ferrari and Kisook couldn't immediately be reached.
More than 60 others suffered injuries in the early morning crash.
Federal investigators plan to upright the Metro-North cars to check for any other possible victims Sunday night.
Officials say the accident is the second passenger train derailment in six months for Metro-North — and the first passenger deaths in an accident in its nearly 31-year history.