Spanish police say they have seized more than 800kg (1,760lbs) of cocaine from a lorry disguised as an official backup vehicle for the Dakar rally.
The lorry was infiltrated into the race, which now takes place in South America, and loaded with cocaine before being shipped to Spain, police said.
The final destination for the drugs was the Spanish island of Ibiza, home to a major drugs trafficking ring.
Police said the cocaine was cleverly hidden in false bottoms in the lorry.
The vehicle was sent from Bilbao in Spain to Argentina where it was loaded with the cocaine during a stage of the famous auto and motorcycle rally, held from 1-16 January.
It then followed the race to its conclusion before being shipped back to Bilbao, where it was seized by police when it arrived on Friday.
"The vehicle had been totally transformed to adapt it to its supposed participation in the competition as a support truck, with publicity and logos of the event painted on its side," a police statement released on Tuesday said.
In a joint operation with police in Argentina, Spanish police arrested seven suspects in Bilbao, Barcelona and Ibiza, all of them Spaniards.
Police said they were all members of a major drugs trafficking ring which was trying to smuggle the cocaine to the Balearic island of Ibiza in time for its famous summer party season.
The police said they also seized 15,000 ecstasy pills, hashish, guns and 47,000 euros (£41,500; $64,000) in cash.
Another 6,000 euros and false documents were found in an apartment in Barcelona that police suspect was used by the alleged head of the smuggling ring.
The Dakar rally was switched from Africa to South America in 2009 over security fears.