MADRID (Reuters) - Spanish authorities have destroyed 415,000 hemp plants worth up to 100 million euros ($108 million) in an operation to dismantle what police said on Wednesday was Europe's biggest cannabis plantation.

       Around 50 tonnes of the plants were being dried in a warehouse for processing into cannabidiol (CBD), a non-psychoactive compound that is increasingly used to treat anxiety, insomnia and other ailments.

       Located in the rural northern region of Navarre, the plantation was spread across 11 fields with a combined area of 67 hectares (166 acres), the Guardia Civil force said in a statement.

       While CBD sale and consumption is legal across Spain and most of Europe, Spanish law still prohibits the cultivation of cannabis plants for anything other than industrial uses, such as for textiles and seeds, according to the Agriculture Ministry.

       Growing hemp for conversion into CBD or other derivatives remains a criminal offence.

       Three people were arrested as a result of the operation, which began in mid-2021 when police discovered one of the fields.

       The Guardia Civil said the plantation owner initially presented the farm as a legal operation to produce industrial cannabis but was later found to be planning to export large quantities to Italy and Switzerland for processing into CBD.

       ($1 = 0.9237 euros)

       (Reporting by Nathan Allen, editing by Andrei Khalip and Tomasz Janowski)