A spokesman for Muhammad Ali said the former heavyweight champion is being treated in hospital for a respiratory problem.
Bob Gunnell said Ali is being looked after by doctors as a “precaution” and added that the 74-year-old is in “fair condition”. A brief stay is expected but he declined to identify the hospital or when Ali was admitted.
Ali has had Parkinson’s disease for a number of years. He retired from the ring in 1981.
He was admitted to hospital in December 2014 with what was believed to be a mild case of pneumonia. Doctors later determined he was actually suffering from a severe urinary tract infection, for which he received further treatment in hospital in January 2015.
In recent years, he has kept a low profile and his last public appearance was in April at the ‘Celebrity Fight Night’ gala in Arizona, a charity that benefits the Muhammad Ali Parkinson Centre.