UNDATED (AP) — Former world heavyweight boxing champ Muhammad Ali remains in a Phoenix area hospital with what two people familiar with his condition say may be more serious problems than his previous hospital stays. They say the 74-year-old boxing great is fighting respiratory issues that are complicated by the Parkinson's that he was diagnosed with in the 1980s.

The two spoke separately to The Associated Press on Thursday, describing Ali's condition as concerning to family members. They declined to be identified because they were not speaking on behalf of the family.

Ali has been hospitalized several times in recent years, most recently in early 2015 when he was treated for a severe urinary tract infection initially diagnosed as pneumonia.