The State inquiry examining decades of alleged physical and sexual abuse of a seriously disabled woman known as ‘Grace’ has uncovered hundreds of “very revealing” documents into the case.

The Farrelly Commission confirmed the development in its latest update report, saying it has received 6,000 pieces of correspondence in recent months which are helping it with its investigation.

In its fourth report on the work of the behind-closed-doors investigation, senior counsel Marjorie Farrelly said the inquiry has interviewed 101 witnesses in an attempt to uncover what happened.

Ms Farrelly also said that a number of witness statements and interviews have had to be rearranged on a number of occasions “due to issues of ill health, frailty”, and other private matters affecting those involved.

The State investigation is examining why Grace was left in a foster home in the south-east for more than two decades despite consistent evidence that she, and potentially other vulnerable children, were being physically and sexually abused.

The investigation is also examining what monitoring of the placement, if any, was made by gardaí and health service officials, what impact political representations by the family had on Grace not being removed, and if key information was suppressed.

Ms Farrelly said the inquiry has also been given more than 6,000 pieces of correspondence since its last report in September, with the disclosures proving to be “an onerous task but a very rewarding one”.

While the 10-page update report did not provide any details on the exact nature of the new information being uncovered, Ms Farrelly’s report stated that progress has been made on a number of matters, including:

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Why the family at the centre of the alleged abuse were cleared to become foster parents;

The role of the gardaí;

The fostering process;

The care of Grace;

Why Grace was not removed from the family when concerns were raised in the mid-1990s;

What occurred after July 2009.

In addition, the report said the commission is seeking to speak with more witnesses. The report is the latest in a string of updates on the progress of the Grace inquiry, which is due to be concluded in a number of months.

The State inquiry was launched in 2016 — delaying the general election by 24 hours — on the back of a series of reports by the Irish Examiner uncovering the case in 2014 and 2015.