The incredible details of three-time heavyweight champion Ali's final moments were made public by his daughter Hana in an emotional post on Twitter.
"Our hearts are literally hurting. But we are so happy daddy is free now. We all tried to stay strong and whispered in his ear, you can go now. We will be OK. We love you," said Hana Ali, an author and a freelance writer.
"All of his organs failed but his HEART wouldn't stop beating. For 30 minutes ... his heart just kept beating. No-one had ever seen anything like it. A true testament to the strength of his Spirit and Will!" Hana wrote.
Prince doing his version of Daddys levitating magic trick act! pic.twitter.com/ckDQf9XBVt- Hana Ali (@Hanayali) June 5, 2016
His official cause of death was septic shock due to "unspecified natural causes", said family spokesman Bob Gunnell.
The fighter had suffered for 35 years with Parkinson's disease, diagnosed three years after his retirement in 1981.
Ali received a bevy of honours during his lifetime, including the Presidential Medal of Freedom - the highest civilian award of the US.