Poor conditions off the Mayo coast have again impeded the search for the black box recorder from Coast Guard Rescue Helicopter 116. 

Heavy swells around Blackrock have prevented boats from getting near the site where a signal from the recorder has been detected.

Rescue crews are hopeful that they can identity its exact location and that this will be in or beside the wreckage of the Sikorsky S92 helicopter that crashed in the early hours of Tuesday morning.

It is thought that preparatory work to investigate the location in more detail might be carried out over a few hours tomorrow, during a forecast break in the bad weather.

But it is likely to be early next week before more detailed underwater examinations can take place.

In the meantime, shoreline searches are continuing along some 20 kilometres of the north Mayo coast from Blacksod to Annagh Head.

Gardaí have advised those involved in these searches that they should not attempt to handle any gas canisters from the helicopter that may have washed ashore.

Some other debris from Rescue 116 has washed up on the Inishkea islands, a short distance from Blackrock, where the helicopter crashed.

Efforts to recover this material will also be made in the coming days.

Captain Dara Fitzpatrick, the only one of the crew to be recovered so far, was found critically ill in the water on Tuesday and later confirmed dead. Her funeral was held in Dublin earlier.

Captain Mark Duffy, Winch Operator Paul Ormsby and Winchman Ciarán Smith all remain missing.