More than three tonnes of cocaine has now been recovered from an ocean-going tug that was intercepted by the Royal Navy last week.

The National Crime Agency (NCA) revealed the quantity of illegal substances found aboard the vessel in a press statement on Thursday, a week after the tug was first detained.

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If cut and sold in the UK the drugs are believed to have had a likely street value of more than £500m, depending on purity.

The vessel was taken to Aberdeen harbour where a search began led by Border Force officers with specialist deep rummage skills.

NCA senior investigating officer John McGowan said: “The search of this vessel has been lengthy and painstaking, undertaken by hugely skilled specialists working in difficult conditions.

“The result is this massive discovery – believed to be the biggest single class A drug seizure on record in the UK, and likely to be worth several hundred million pounds.

“Our investigation continues, but the operation was only possible thanks to the close co-operation between the NCA, Border Force, the Royal Navy, plus the French DNRED and our other international partners. The extensive operation in Aberdeen was given substantial support from Police Scotland.”

The nine-man crew of the Hamal, all Turkish nationals aged between 26 and 63, have been charged with drug trafficking offences.

They appeared before Aberdeen Sheriff Court on Monday 27 April where they were remanded in custody until their next appearance on Tuesday 5 May.