The Guardia Civil say they have dealt a severe blow to the illegal hashish distribution network in Andalucía.
Twenty people were arrested in a coordinated operation this week and hundreds of thousands of euros in cash seized.
Sources close to the investigation said that 300 officers took part in 24 raids early on Wednesday morning in the provinces of Seville, Malaga, Granada, Huelva and Cadiz.
In the Campo de Gibraltar area, eight property searches were carried out in Algeciras and Tarifa.
The focus of the operation was the logistics organisation supporting the smuggling of hashish across the Strait of Gibraltar. The Royal Gibraltar Police also helped with the investigation.
Among those held were experts in maintaining the speed boats used to move drugs from Morocco to the Spanish coast.
The Guardia Civil has warned that, because of police pressure on the Strait, gangs are now trying to land their shipments further along the coast.