Gardai have not responded directly to claims that one of its informers was present when Jean McConville was shot and secretly buried by the IRA.
Mrs McConville was abducted from her west Belfast home, shot in the head and buried on a Co Louth beach in 1972.
She was later accused of being an informer, a claim rejected by her family.
While the IRA initially denied involvement in her disappearance, it eventually admitted its role in 1999 when the Independent Commission for the Location of Victims’ Remains (ICLVR) was established.
Her remains were recovered from a beach in Co Louth in 2003.
Ms McConville was one of 17 people killed and secretly buried by republicans during the Troubles who are known as the disappeared.
A new book by veteran journalist Martin Dillon contains the revelation that a Garda informer helped dig her grave and was present when the mother-of-ten was shot dead.
Mr Dillon also claims that the informer was the son of a senior IRA man who was allowed to leave Ireland when he was eventually unmasked as working for the state.
If true, the explosive claims pose serious questions over what authorities in the south knew about the missing mother during the three decade search carried out by her loving children.
Gardai were asked if they knew Mrs McConville had been shot and where she was buried but did not respond directly.
They were also asked if he force provided any information regarding the whereabouts of Mrs McConville’s body to her family or the Independent Commission for the Location of Victims’ Remains.
Again, no direct response was provided.
In a statement the force said: ”An Garda Síochána does not comment on the detail of ongoing investigations.
“Anyone with information on this matter should bring it to the attention of An Garda Síochána or the PSNI.”
The Department of Justice in Dublin was asked similar questions, including what the Irish government knew, but, like Gardai, did not respond directly.
In a statement a spokesman said the murder of Mrs McConville was “an appalling act with no justification”.
“Clearly it would not be appropriate for the Department to offer any comment on the views or allegations made in the context of material published by third parties,” he said.
“Dealing with the legacy of the Troubles on this Island is a complex and sensitive task, and one to which there are no easy solutions.”
He added the establishment of the ICLVR by the Irish and British governments “was a very significant step which recognised the particular cruelty endured by the families of the disappeared, facing not only the tragedy and injustice of losing a loved one to murder, but not knowing for decades where that loved one was buried.
“The commission is independent in the performance of its functions.
“Confidentiality in respect of the information provided to the commission is fundamental to its work and the commission relies on information in order to pursue its investigations.
“The Government remains fully supportive of the work of the Commission.”
‘The Sorrow and the Loss – The Tragic Shadow Cast by the Troubles on the Lives of Women’ by Martin Dillon and published by Merrion Press is available now.