Jean McConville's son has said he wants justice as police quiz Sinn Féin president Gerry Adams about the killing.
Mr Adams has vehemently rejected allegations made by former republican colleagues that he had a role in ordering the death of mother-of-10 Jean McConville – who was dragged away from her 10 children after being wrongly accused of passing information to the British army in Belfast.
Gerry Adams was detained overnight after voluntarily presenting himself for interview at a police station in Antrim. He can be held for two days without charge.
Mrs McConville’s son Michael, who was 11 when his mother was murdered, welcomed the arrest.
He told the BBC: “We’re just happy to see everything moving as it is moving at the minute.
“Me and the rest of my brothers and sisters are just glad to see the PSNI doing their job. We didn’t think it would ever take place [Mr Adams’ arrest], but we are quite glad that it is taking place.
“All we’re looking for is justice for our mother. Our mother, on the seventh of next month, would have been 80 years of age.
“Although we didn’t spend much time with our mother, we’d have liked to have spent a lot of time with her. If the IRA hadn’t have killed our mother, God knows, she still might have been alive today.”
Sinn Féin has claimed last night’s arrest of Gerry Adams in connection with the abduction and murder of Mrs McConville was “politically motivated” and designed to damage the party and its leader.
Sinn Féin issued a statement, apparently scripted before Mr Adams was arrested, in which he was quoted as saying: “Last month I said that I was available to meet the PSNI about the Jean McConville case.
“While I have concerns about the timing, I am voluntarily meeting with the PSNI this evening.”
He said he believed the killing of Jean McConville and the secret burial of her body was “wrong and a grievous injustice to her and her family”.
“Well-publicised, malicious allegations have been made against me. I reject these,” he said.
“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.”