French police have recovered an ancient golden plate missing for 25 years, part of the world-renowned Lava Treasure, discovered off the island of Corsica, sources close to the case said.

Five people have been arrested, including the go-between who was to deliver the treasure to its buyer, following a transaction between some Corsicans and the seller in Belgium, the sources said.

The Roman treasure of coins and the gold plate, considered one of world’s most important finds, was discovered underwater in the Gulf of Lava, southern Corsica in 1985.

Two brothers who were diving in the waters searching for sea urchins instead came up with several gold coins that they illegally sold.

After interrogating some 500 people, police were eventually able to recover 78 pieces of the treasure – but the star item of a gold plate was still missing.

Authorities have estimated the recovered pieces of the Lava Treasure to be valued at between one and €23 million.

After recent suspicions about a secret sale of another piece from the Lava Treasure, custom authorities along with the office that fights against the trafficking of cultural treasures and Corsican officials launched an investigation which partially ended on October 21 with the transaction in Belgium.

The final transaction never took place. Police, fearing they might lose their target, moved in and arrested the intermediary in the sale at the train station at Paris’ Charles de Gaulle airport.

As a cultural treasure, the golden plate belongs to the state and should be turned over to the culture ministry in December.