American boxing legend Muhammad Ali has spent the second day in a hospital Friday, fighting a respiratory infection.
The Associated Press reports that people familiar with his condition say he may be battling more serious problems that are concerning to family members.
Earlier Friday, the champion's spokesman Bob Gunnell downplayed the news, saying Ali was in "fair condition" while under the care of doctors in the Phoenix, Arizona, area.
Ali, who retired from boxing in 1981, has had Parkinson's disease for three decades. Despite the disease, he kept up a busy appearance schedule until recently, though he has not spoken in public for years.
Doctors say the Parkinson's likely was caused by the thousands of punches Ali took during a career in which he traveled the world for big fights.
He has been hospitalized many times, most recently in early 2015 for a severe urinary tract infection initially diagnosed as pneumonia.
News of his hospitalization brought well wishes from boxers and others on Twitter, including Sugar Ray Leonard, who modeled his career after Ali's.
"Prayers & blessings to my idol, my friend, & without question, the Greatest of All Time @MuhammadAli ! #GOAT,'' Leonard wrote.