Spanish police seized 6.5 tons of cocaine from a boat off the Canary Islands, which are near Africa, and arrested nine people after a U.S. tip-off.

The police announced on Sunday that the boat, which was flying a Tanzanian flag and had departed from Panama en route to Vigo, Spain, was intercepted 600 miles off the Canary Islands on Wednesday, CBS News reported.

The narcotics were hidden in the hold of the boat, which had unusual structures on board that concealed the narcotics, police said.

The Drug Enforcement Administration provided key "information" that aided the successful operation, according to Spanish police.

Spain is a main gateway for cocaine to enter Europe, because of its ties with Latin America, where the drug is produced, and its location on the European continent.