Speaking by video-link, their images blurred and their voices distorted, and referred to only by code names, the inspectors said that they were contacted by the DEA, which asked them to carry out a "monitored handover" with the aim of "dismantling an international organisation" engaged in drug trafficking and "identify" people suspected of forming part of a criminal network "as high as possible" in its hierarchy.

The US officials had acquired the cocaine from alleged traffickers in South America, also in an undercover operation, the inspectors said. It was then transported to Portugal in a "normal commercial flight".

The PJ kept the drugs for some five days, after which they were to transfer it to the suspects on a fishing boat at sea.

On 20 August of 2015, the sailing boat on which the inspectors were travelling contacted the suspects' boats with a view to making the drop of some 60 bundles of cocaine, which was done.

After the transfer, the undercover vessel moved away and the suspects' boat was intercepted by the Portuguese coastguard and air force, the inspectors explained.

"It's not normal for an undercover action of this nature to be revealed in procedural terms," said Carlos Melo Alves, the lawyer for the five accused - all fishermen by trade. "What happened is that the drugs were transported from South America by the US authorities, and handed over to the PJ, which kept them at an unknown location, got themselves a vessel and delivered [the drugs] to these fishermen.

"This from a technical and even ethical point of view raises many questions," he said, adding that the revelations bring into question whether "even so these fishermen committed the crime of trafficking".

In view of the new information, the judge ruled that further hearings must be heard. The trial began in early January.

At the first hearing in the trial, three of the five accused admitted agreeing to carry out the transfer of the cocaine on the high seas, having been offered payment to do so.

The other accused admitted having been approached to transport the "packages", which they said they were to receive out at sea and take to the port at Nazaré.

The trial is to resume on 6 April.