A homeless man died after cops found him lying unconscious on Manhattan subway tracks early Saturday, police said.

The unidentified man, believed to be in his 50s, was found on the downtown No. 6 train tracks at the 125th Street station in East Harlem around 1:20 a.m., cops said.

First responders carried the man onto the platform, where they performed CPR before rushing him to Harlem Hospital, where he was pronounced dead.

The man was not hit by a train, police said. He may have had a heart attack, according to police sources.

The city medical examiner will determine the official cause of death.