The Air Accident Investigation Unit has issued a statement to mark the fourth anniversary of the R116 helicopter crash, in which four Coast Guard crew members were killed.
The aircraft crashed into Blackrock Island, off the north Mayo coast, on 14 March, 2017.
The remains of two of the crew - Captain Dara Fitzpatrick and Captain Mark Duffy - were found in the weeks that followed, but the bodies of two others, Winch operator Paul Ormsby and Winchman Ciarán Smith, remain lost at sea.
The AAIU is obliged to provide an update on the progress of its inquiries, in the event that the final report is not published within 12 months of an investigation being launched.
A brief statement this afternoon confirms that a review into the draft final report is still ongoing and, as a result, the investigation process has yet to formally conclude.
The review was ordered after one of the parties mentioned in the draft report raised concerns about elements in the document.
The review is being conducted by Patrick McCann SC.
It is understood it is likely to continue for several more weeks.
The AAIU's final report regarding the accident will not be published until the work of the Review Board is complete.
