The Air Accident Investigation Unit has said initial indications are that there was no mechanical failure in the moments before Coast Guard Rescue Helicopter 116 crashed off north Mayo last month. 

The AAIU said that although the investigation is still at a preliminary stage they have issued the statement as they are "mindful that Sikorsky S-92A helicopters are in operation around the world in a variety of roles, including Search and Rescue".

"Following an event such as this, many operators and agencies are anxious to learn if any matters are identified during the ongoing investigation that may require immediate safety actions," added the statement.

"An initial analysis has been conducted of the data retrieved from the helicopter’s Health and Usage Monitoring System (HUMS) and the Multi-Purpose Flight Recorder (MPFR). No mechanical anomalies have been identified during this initial analysis," said the statement.

The AAIU said the investigation is ongoing and a preliminary report will be issued in the near future.

Coast Guard helicopter Rescue 116

Meanwhile, efforts to lift the wreckage of R116 have been delayed again due to rough sea conditions around Blackrock Island.

Paul Ormsby and Ciarán Smith have been missing since Rescue 116 was lost in mid-March.

The body of Mark Duffy was recovered from the wreckage and Dara Fitzpatrick died a short time after being rescued.

North west winds and a three-metre swell made it unsafe for divers to descend to the wreckage 40 metres below sea level today. 

A further assessment will be carried out in the morning, as attempts to bring the helicopter to the surface continue. 

Divers have to first attach a bridle to the helicopter wreckage before it can be lifted to the surface. 

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The helicopter wreckage is located in waters off Blackrock Island, around 10 miles off the Mayo coast.

Efforts to access it have been complicated by strong currents and spring tides in recent days. 

An attempt to tilt the aircraft, using inflatable lifting bags, had to be abandoned when conditions proved too challenging for Naval Service divers to operate in. 

Now, search co-ordinators plan to lift the wreckage directly from the sea bed and bring it to the surface. 

A specially equipped tug has travelled to Blacksod from Castletownbere, Co Cork, to assist in the operation. The Ocean Challenger vessel will be positioned directly above the helicopter, which is lying against a rock 40m below sea level. 

Naval Service divers were to attach a bridle to the aircraft this morning before an attempt was to be made to bring the wreckage to the surface this afternoon.

The operation will be monitored by the Marine Institute's Holland 1 Remotely Operated Vehicle (ROV).

Search teams are anxious to see if there is any trace of the missing crew members in an area directly underneath the wreckage. 

The helicopter will ultimately be transferred to the AAIU facility in Gormanston, Co Meath.