The official cause of death was “septic shock due to unspecified natural causes,” Gunnell said, adding that Ali was first hospitalized on Monday.
“We still had a lot of hope it was going to turn around,” he said, but it later became clear that the boxer’s condition was deteriorating.
“No one had even seen anything like it,” Hana Ali wrote on Instagram.
She said the family was surrounding Ali, hugging and kissing him, holding his hands and chanting an Islamic prayer while his heart kept beating as his other organs failed.
She called it a “true testament to the strength of his spirit and will”.
Former US president Bill Clinton, comedian Billy Crystal and sports journalist Bryant Gumbel will offer eulogies for Ali, the three-time world heavyweight champion who died on Friday at age 74 after a long battle with Parkinson’s disease.
A small family funeral will precede the public service on Thursday, spokesman Bob Gunnell told reporters in Scottsdale, Arizona.
“A rather large funeral procession will take Muhammad Ali through the streets of Louisville to allow anyone that is there from the world to say goodbye,” Gunnell said.
He noted that Ali himself had requested much of the planned service, which is to be conducted in accordance with “Muslim tradition” and in the presence of an imam.
That public parade will end at Cave Hill Cemetery, where Ali will be buried.
“His final hours were spent with just immediate family,” he added. “He did not suffer.”
Ali’s body was to be brought back to Louisville “within the next 24 to 48 hours,” Gunnell said.
President Barack Obama led tributes from around the world to the iconic fighter, one of the great sports heroes of the 20th century and a colorful civil rights activist.
Louisville lowered flags to half-staff in his honor on Saturday.