Spanish police seized 4.5 tonnes of cocaine with an estimated street value of €105m after raiding a cattle ship off the Canary Islands earlier this week, a statement said on Saturday.
The ship had stopped at ports in about a dozen countries before Tuesday's raid, and police said drug smugglers had started using livestock ships because it was more difficult for police to trace their illicit cargo.
"International organisations are reinventing themselves to transport drugs from Latin America to Europe, using livestock to make the control and localisation more difficult," the Spanish police statement said.
Police arrested 28 crew members on the Togo-flagged Orion V, which had been trailed from Colombia in an operation by Spanish authorities, the US Drug Enforcement Administration and Togo police.
Officers unloaded dozens of boxes containing the cocaine on the port side in Las Palmas on the island of Gran Canaria.