The Los Angeles Times and TMZ were reporting Thursday that cult leader Charles Mason, 83, was hospitalized with an unknown condition.
Citing medical privacy rules, the California Department of Corrections and Rehabilitation said it CBS News it could not "confirm or deny this information" when asked about Manson's hospitalization.
Manson shocked the country half a century ago by ordering members of his cult to carry out a wave of murders -- allegedly aimed at inciting racial conflict.
Known as the "Manson Family," the mostly young, female members of the cult killed seven people.
Manson is serving nine consecutive life sentences at California State Prison, Corcoran, for his role in the killings.
Among the victims was Sharon Tate, a pregnant actress who was then married to filmmaker Roman Polanski. She was stabbed 16 times by Manson's followers.
Amid similar reports of hospitalization in January, a state corrections official would confirm only that the 82-year-old killer was still alive.
Manson was convicted of leading the cult -- in which disaffected young people living in a commune followed his orders and were ultimately turned into killers.
Manson and three female followers, Susan Atkins, Patricia Krenwinkel and Leslie Van Houten, were convicted of murder and sentenced to death for killings at two gruesome scenes in the summer of 1969. Another defendant, Charles "Tex" Watson, was convicted later.
All were spared execution when a U.S. Supreme Court ruling temporarily banned the death penalty in 1972.