Details have emerged of the questions that Gerry Adams is being asked about the murder of Jean McConville.
The Sinn Féin leader has been held by the PSNI since Wednesday evening, when he arrived at a police station in Antrim by appointment to give evidence.
Mother of 10, Jean McConville, was abducted and executed by the IRA in 1972.
Sinn Féin's policing spokesperson Gerry Kelly has been speaking to Mr Adams and his legal team this afternoon and he says that the PSNI have been questioning Mr Adams on "open source material".
Mr Kelly said: "They (the PSNI) have been producing photographs that might be 40 years old and that are in the public arena. They have actually been referring to a book that is out now 20 years and newspaper articles that are decades old."
The North's Deputy First Minister Martin McGuinness has dismissed claims made by Peter Robinson that he is attempting to blackmail the PSNI.
Mr McGuinness says Sinn Féin unequivocally support the police services North and South of the border, but the party reserves the right to challenge the PSNI where they feel mistakes have been made.