The pioneering singer was administered CPR by paramedics, and taken to hospital, where he was pronounced dead after an hour.
The cause of his death has not been revealed as yet.
Hayes, along with Al Green, James Brown and Stevie Wonder, was one of the biggest black musicians of the early 1970s.
The musician even won Academy and Grammy awards for his relentless rendition of "Theme From Shaft".
This was the time when, with his deep voice, he laid the groundwork for genres including disco, contemporary urban music and rap as well as romantic crooners such as Barry White.
It was in 1997 that he became the voice of Chef, the sensible school cook and devoted ladies man on the animated TV show South Park.
The character won him great accolades, but he quit the show in 2006 in anger after an episode mocked his Scientology religion.
"There is a place in this world for satire, but there is a time when satire ends and intolerance and bigotry towards religious beliefs of others begins," the Telegraph quoted him as saying.