Spanish police Monday said they had captured three drones that could transport large amounts of drugs from Morocco to Spain. They also arrested a gang believed to be manufacturing the drones.

According to a police statement, officers seized three “drone submarines” that were being built and detained eight Spanish citizens.

It stated that three of them — one of which was almost finished and two were in construction — would be delivered to French drug dealers for large amounts of cocaine transport.

Police posted a video of the seized drones to social media, and stated that each drone could hold up to 200 kg (440 pounds) worth of product.

Desmantelada una organizacion que fabricaba #drones y #semisumergibles capaces de cruzar el Estrecho con hasta 200 kg de drogaHay 8 personas detenidas en #Cadiz, #Malaga y #Barcelona1a vez que se intervienen vehiculos que operan bajo el agua sin tripulacion a bordo pic.twitter.com/P81cRwjIVx

According to police, it was the first time that they had ever seized these devices. Officially known as unmanned underwater vehicles (UUVs),

The statement stated that “these devices could enable drug traffickers to remotely transport large quantities of drugs across the Strait of Gibraltar.”

Police also seized several large UAVs manufactured by the gang with 12 motors and a range exceeding 30 km. This was more than enough to cross a 15-kilometer (nine mile) stretch between Spain and Morocco.

Officials said that the gang also made false bottoms to transport drugs.

Police said that one of the drug-laden vehicles was “intercepted while it was traveling to Denmark aboard a truck with the intent of avoiding any police checks.”

Police said that they were targeting criminal gangs from Spain, France, Italy, and Denmark.

Spain’s proximity to Morocco, a major producer of hashish, and its close ties to former colonies in Latin America have made it an important entry point for drugs headed for Europe.

The 14-month-long operation ended with eight arrests, according to police. Six detainees were arrested on charges of drug trafficking and belonging a criminal group.