The Oscar Award and Grammy-winning singer went into the hospital Tuesday night, Hayes' longtime song-writing partner David Porter told the Memphis Commercial-Appeal.
"He's just overworked and had been in Atlantic City performing, the D.C. area performing, and in Tunica (Miss.) a couple of nights ago," Porter said. "He was just overworked. That's it in a nutshell."
Hayes, 63, is best known for his 1971 No. 1 hit "Theme From Shaft," which won the Oscar for best song. His score for the movie earned two Grammys and he is the voice of "Chef" in the animated cartoon series "South Park."
Hayes was inducted into the Rock and Roll Hall of Fame in 2002.