The 65-year-old republican leader was arrested last night over the killing of mother-of-ten Jean McConville after voluntarily attending a police station in Antrim, Northern Ireland, for an interview.
Adams strongly rejected any involvement in the murder - one of the most infamous incidents in Northern Ireland's violent history - saying in a statement that the allegations were "malicious".
"While I have never disassociated myself from the IRA and I never will, I am innocent of any part in the abduction, killing or burial of Mrs McConville," he said.
The party now shares power with the pro-British Democratic Unionist Party (DUP) in the devolved government in Belfast. It is also represented in the Irish parliament in Dublin.
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McConville, a 37-year-old widow with ten children, was snatched from her home in west Belfast, becoming one of more than a dozen so-called "disappeared" of the conflict. She had been shot in the back of the head.
McConville's son Michael, who was 11 years old when he saw his mother dragged away, said he was pleased that the police were "doing their job".
However, he admitted in a BBC interview that he still refused to name the people he saw taking his mother, saying he still feared reprisals.
"If I told the police a thing either me or one of my family members or one of my children would get shot by these people," he said.