The AP cited a Nevada prison official as having confirmed Simpson's release. No details on Simpson's whereabouts or destination were reported, and authorities could not be reached to verify the report.
Simpson, 70, won his freedom from a Nevada parole board in July after nine years behind bars, at a hearing that did not take into account his 1990s trial for the murder of his ex-wife Nicole Brown Simpson and a friend, Ron Goldman.
He reportedly left prison shortly after midnight local time.
Simpson, a former pro football star turned actor and TV pitchman, was found not guilty in 1995 following his sensational, 13-month trial in Los Angeles, which was televised live daily, transfixing much of the nation.
A civil court jury subsequently found him liable for the deaths and ordered him to pay $33.5 million in damages to the victims' families, a judgment that remains largely unpaid.
Simpson's ultimate destination remains unclear. He told parole board members he hopes to move to Florida, where he has friends and family, a plan that must be approved by probation authorities there.
Florida corrections officials say they had not received a parole transfer request for Simpson and had not been contacted by their counterparts in Nevada.
Simpson is a native of California, born in San Francisco, and played his final years as a pro football player for that city's team, the 49ers. He lived in Los Angeles at the time of the murders.
But California corrections officials say he has not filed papers to live in that state either.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)