No details of the crew have so far been released, but it is understood that, although the boat operated out of Aberdeen, three come from the Anstruther/Pittenweem area. The fourth man is thought to come from Aberdeen.

It is also understood the vessel was not involved in fishing at the time, but was doing oil related work.

Steve Quinn, Aberdeen Coastguard Watch Manager said there is “extreme concern” for the safety of the four.

He added that relatives were being kept up to date, but the discovery of debris is not a good sign.

Bertie Armstrong, chief executive of the Scottish Fishermen’s Federation, said, “There are families with their hearts in their mouths right now. We’re desperately waiting for news.”

An RAF Nimrod search and rescue aircraft was leading the search along with a Sea King rescue helicopter from Stavanger in Norway.

Three other fishing boats joined the search, which was started in hurricane force 11 conditions with winds gusting up to 80mph.

The alarm was raised late last night when staff at the RAF rescue centre at Kinloss picked up a distress beacon.

The location was fixed at 160 miles east of Aberdeen on the boundary line with the Norwegian sector of the North Sea.

The search for the boat continued throughout the night and was stepped up when daylight came with a second Sea King from RAF Boulmer in Northumberland.

The vessel was equipped with two lifeboats and all crew had survival suits.

The manager of the Pittenweem-based Fishermen’s Mutual Association, Billy Hughes, said people in fishing communities always take things very personally when there are reports of incidents at sea and the possibility of lives of anyone in the industry being lost.

“It hits us a great deal harder when these incidents involve people we have known all our lives,” he said.

In Anstruther itself the mood of local people was sombre.

Scott McAuslan (31), who lives near the harbour, said the news had shocked the town.

He said, “I hope they do find them, but I think they’ve been looking for the boat for a while. It’s a small town, the type of place where people know each other, so it’s something that will affect folk.”

Ian McGlashan (61), of East Green, said, “It’s a terrible thing. Everyone I’ve been speaking to has asked if there’s any news. The families must be in a state, not knowing what is happening.”

The secretary of the community council, Martin Dibley, who is a local shopkeeper said at the moment there is only speculation about who is involved, adding it would not be appropriate to comment.

Meanwhile, Liberal Democrat leader Sir Menzies Campbell, the MP for North East Fife, said local people were all praying for the fishers safe return.

Sir Menzies cut short discussions with campaigners for family rights in London to return to his office and monitor developments.

He said, “At the moment the whole community is praying these men will be found safe. We should never forget just what risks the fishing industry undertake on a daily basis.”