Police in Spain have seized nearly a tonne of cocaine, which was found hidden inside fake stones.

Eleven people have been arrested.

The Policia Nacional says the investigation began more than a year ago, when detectives noted meetings between known drug traffickers, some of whom had contacts with a company dedicated to the stone business.

Police say the industry is known for its link to drug cartels in South America.

Officers tracked a shipment coming from Ecuador with 12 containers of stones, with an approximate gross weight of 188,000kgs.

After passing through Cartagena de Indias, Colombia, the vessel arrived at the port of Barcelona and was moved to Zaragoza, later arriving at an industrial warehouse in Humanes, Madrid.

Police carried out the arrests while the group was working to extract the drug from the stones.

They found 785 packages of over 1kg of cocaine concealed inside the stones.