Melissa Reid and Michaella McCollum Connolly were arrested at Lima airport in Peru as they went to board their flight back to Spain with 11kg of cocaine worth €1.6 million in their luggage.
The pair told Lima police they had been shadowed by gang members throughout the trip to coerce them into committing the crime.
But Ibiza police are not convinced by the 20-year-olds' claims, judging that the girls have come to form part of the island’s expat drug trafficking scene.
“In my experience I don’t think these two girls were forced to do this because, particularly when you go to South America, you need to pass several controls, First Sergeant Alberto Arian Barilla told British newspaper the Daily Telegraph.
“The first thing you do is go to the passport control and say: 'Listen, this is what is happening to me.’ The policeman will react, so I don’t think they were forced.”
The pair could spend up to three years in prison before a trial, where they will face sentences of up to seven years if found guilty.