In a statement this evening Rush Credit Union says the board appointed Grant Thornton to carry out an independent review in February 2016.
The external review process is nearly complete and a report is being prepared for the Board.
The Credit Union says it continues to operate as normal, adding there is no implication for the savings of any of account holders
The Credit Union at the centre of a possible financial irregularity has written to members to reassure them their money is safe.
€700,000 is understood to have disappeared from Rush and Lusk Credit Union.
The Irish League of Credit Unions has moved to reassure members that no credit union funds will be affected and that they're fully insured against such matters.
Meanwhile, a Central Bank Spokesman has said it is working with the Credit Union and said members should continue their business as normal.
Gardaí have confirmed they are investigating an irregularity at a financial institution in north Co Dublin.
It is understood to relate to the suspected disappearance of €700,000 from Rush and Lusk credit union.
A spokesman for the Credit Union has reassured customers that their money is safe.
"The credit union has identified an issue," a statement from the Irish League of Credit Unions read.
"As the matter is currently being investigated we cannot comment in any great detail other than to say that the credit union is working extremely hard to ensure that this matter is dealt with swiftly.
"The credit union has written directly to members on this issue.
"We would like to reassure members that no credit union funds will be affected by the incident and that the credit union is fully insured to deal with such matters.
"Operations at Rush Credit Union have not been disrupted and members can do business with the credit union in the usual way."