Three men being quizzed after being caught in a yacht off the Irish coast with cocaine worth more than half a billion euro (£403m) are suspected mules.

Top drugs squad sources said none of the gang — all thought to be from England — were known associates of major underworld figures.

“If they were big players we would all know about it at this stage. We would know by now if they were significant,” said one source close to the investigation.

But security chiefs across Europe were “popping champagne corks” at the record-breaking haul masterminded by an international agency in Lisbon, Portugal, one Irish Government official said.

As detectives detained the three men for a second night, officers revealed the 75 plastic-wrapped bales, weighing around 20kg (44lb) each, were bound for the streets of mainland Europe.

The stash from the 60ft Dances With Waves yacht, which was intercepted 170 miles off the south-west coast, was removed under armed guard from the vessel in the busy fishing port of Castletownbere, Co Cork.

Superintendent Pat Byrne of the Garda National Drugs Unit said the haul was a massive blow to organised crime.

“The significant amount of cocaine would probably indicate that wider Europe would have been at least partly the market for this product rather than the Irish market alone,” said the officer.

The record-breaking haul could total 1.7 tonnes, and depending on purity could be worth as much as €700m (£572m).

Last year 1.5 tonnes of cocaine valued at €440m (£323m) washed up on the Cork coast near Mizen Head after an elaborate trafficking scam fell apart.

Stormy weather conditions earlier hampered the recovery of the luxury 60ft yacht, which was almost crippled with damaged sails and boom, and sailed for almost 30 hours to shore under escort.

Armed officers patrolled the quayside as the yacht was stripped and the haul loaded on to the harbour before being escorted to nearby Garda stations.

It will be transferred to Garda Headquarters in Dublin’s Phoenix Park for a full forensic examination later.

Commander Eugene Ryan of the Irish Navy said it was a dangerous operation for the armed teams who boarded the 60ft McGregor sloop.

“On a scale of one to 10, and 10 being the most serious, I would class this an eight to nine,” he said.

The three men gave themselves up without any struggle, he added.

The vessel, which was formerly registered in the UK, had been severely damaged in a storm during the Atlantic crossing.

Customs official Brian Smyth said the 75 bales were literally thrown into a storage area, just past the living quarters of the yacht’s hull.

“It’s not something that you can conceal, a large concealment like that in a yacht that size. They were taking up the hatch within the vessel itself,” he said.

“The bales were well wrapped and if there was a question of the bales being possibly dropped at sea they would have survived quite well.

“Essentially we regard and believe it is of extreme high purity.”

The operation was led from the Haulbowline Navy Base in Cork, where naval, custom and Garda chiefs gave instruction via satellite to the LE Niamh.

The yacht had been tracked for up to a month as it sailed from the Caribbean towards the Irish coast, before armed officers stormed it at around 10pm on Wednesday.

Within four hours it was making its way back to land, guarded by the LE Roisin as its sister ship the LE Niamh carried the three suspects to land where they were arrested.

Defence Minister Willie O’Dea praised the operation.

“They boarded that yacht in horrendous weather conditions,” Mr O’Dea said.

“The navy service performed outstandingly as part, of course, of a joint operation involving gardai and customs.”