Ali's official cause of death was septic shock "due to unspecified natural causes"
Muhammad Ali will be laid to rest in his hometown of Louisville in Kentucky on Friday, with a solemn procession carrying his body through the streets where he grew up.
The three-time world heavyweight champion's family have said a public memorial will be held at a sports arena in the city, with thousands set to pay tribute to the boxing legend.
Former president Bill Clinton and comedian Billy Crystal are among those delivering eulogies at the ceremony, which will be led by an imam in line with Muslim tradition.
Representatives of other faiths will also attend, and family spokesman Bob Gunnell said: "The celebration will reflect his devotion to people of all races, religions and backgrounds."
In the coming days, Ali's relatives will accompany his body as it travels to Kentucky from Phoenix in Arizona, where the renowned fighter died on Friday night at the age of 74.
A private service will be held a day before the public memorial, which will be streamed online to fans around the world.
According to Mr Gunnell, Ali's official cause of death was septic shock "due to unspecified natural causes".
Earlier in the week, he had been admitted to hospital with respiratory issues linked to Parkinson's disease, which he had been diagnosed with in 1984.
Mr Gunnell said Ali's wife and nine children had been hopeful that his stay in hospital would be brief, but were called to his bedside when his condition became more serious.
"They had a full day to say farewell to Muhammad. All family members, all daughters and his son were in attendance, and his wife," the family spokesman told reporters.
"They got to spend quality time with him to say their final goodbyes, and it was a very solemn moment. It was a really - you hate to say this - but a beautiful thing to watch.
"Of course there was sorrow, they were in sadness. But it was done - the champ would have been very proud of his family."
Flowers, cards, and signs have been placed outside his childhood home in Louisville, and flags have been flying at half-mast in the city.
Tributes have also been paid to Ali from figures in sport, showbiz and politics, with President Obama saying the boxing icon "fought for what was right" both inside and outside the ring.
Meanwhile, George Foreman has paid tribute to the man who famously beat him in the Rumble in the Jungle.
"He moved around the ring, he had style and class, he was tall and good looking - he belonged to the arts, because he had poetry. He had it all," he said.