A large-scale search operation along the west coast has been unable to locate the two missing Rescue 116 crewmen, but senior investigators said further efforts are being made to find them.
One of Ireland's biggest maritime searches was carried out over the weekend, with more than 100 fishing vessels involved in the rescue operation.
However, recovery teams were unable to find missing winch operator Ciaran Smith (38) and winch man Paul Ormsby (53) following extensive searches from Blacksod, Co Mayo, to Killybegs, Co Donegal.
The crewmen have been missing since their Sikorsky S-92 aircraft crashed 12km off the Mayo coast in the early hours of March 14.
Supt Tony Healy said searches for the two men will continue, with divers from the Garda Water Unit expected to carry out examinations near Blackrock island once sea conditions improve.
"Shoreline searches and surface searches will continue," said Supt Healy.
"The sea search along the west coast has finished and now we're hoping to carry out more underwater scans in some areas when conditions improve."
Some of the volunteers spoke out after they were told to pay motorway tolls as they returned from the search site.
Michael Hickey, a spokesman with Carrick River Rescue, said his voluntary organisation is dedicated to finding the men, but they do not believe they should be charged the M7 tolls.
"We raise our own funds, we have a second-hand shop in Carrick-on-Suir and the girls running it are voluntary too - nobody in our organisation gets one cent for what they do, nobody gets paid," he said.
"They do it because they want to do it and they want to help families in trouble."
The family of Ciaran Smith have called on local fishermen with intimate knowledge of the seas in the search area to help bring their loved one and his colleague home.
Gerard O'Flynn, operations manager with the Irish Coast Guard, has thanked all organ- isations involved for their unstinting support over the past four weeks.
He paid special thanks to coast guard, RNLI and Civil Defence volunteers and Defence Forces, including naval divers, ships and Air Corps.
He added that the operation highlighted the value of inter- agency co-operation.