Melissa Reid, from Lenzie, East Dunbartonshire, and Michaella McCollum Connolly, from Northern Ireland, are accused of attempting to smuggle cocaine worth an estimated £1.5 million out of South America. Reid and McCollum Connolly, both 20, were arrested at Jorge Chavez International Airport in Lima after the drugs were found hidden inside their suitcases.
They were trying to board a flight to Madrid on August 6. Police said they found more than 11kg of cocaine in food packaging in the women's luggage.
If convicted, they could face lengthy sentences in an overcrowded Peruvian prison.
However, Spanish police said they had several opportunities to alert authorities.
Alberto Arean Varela, head of the anti-drug and organised crime police unit in Ibiza, said the claims went against his knowledge of trafficking cases.
He said: "Sincerely, with my experience, I don't think these girls were forced to do this. Because, particularly when you go to South America, you need to pass several consuls. 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, who had been on holiday and working separately in Ibiza, have claimed they were forced into drug-running after being duped by a mysterious Cockney they met on the island, who then handed them over to armed Colombians. They said their passports and mobile phones were confiscated.
Both women said they were unable to go to the authorities because the gang had threatened to kill their families if they did not co-operate.
The National Police of Peru released a video of the women being questioned just after their arrest.
During the interview, Reid says: "I was forced to take these bags in my luggage."
Varela's comments come as Spanish police launch an investigation into the claims.
A Spanish police spokesman said: "The Guardia Civil is investigating about the possible connection of this case in Spain."
Reid and McCollum Connolly are expected to appear in court as early as tomorrow.
Both have claimed they were kidnapped and forced at gunpoint to carry out the drug running after being held captive in Spain for a number of days.
The pair also allege they were forced to carry bags in their luggage and were unaware the 32 food packets contained drugs.
McCollum Connolly's solicitor Peter Madden, who has arrived in Peru, said his client denied involvement in any criminal offence and would be appearing before an examining judge shortly.
However, it is feared legal proceedings could be lengthy.
Madden, one of Northern Ireland's top lawyers, said McCollum Connolly was threatened by a gang of up to 14 men with guns, kidnapped and forced by threat to obtain and carry drugs.
"She wasn't offered any money, she was threatened and held. She is now prepared and ready to give full details to the police," he said, adding that Reid was similarly threatened by the gang.
Madden, who headed up the legal team that represented the majority of deceased and wounded at the Bloody Sunday inquiry, said McCollum Connolly was finding it difficult to cope with the current situation but the women remained optimistic about the outcome.
The pair were formally questioned for the first time on Friday. They are expected to be transferred to the notorious Santa Monica prison, where they will be held until their trial.
Meanwhile, friends back home have started an internet campaign to free them, called FreethePeru2.
More than 1000 supporters have joined the group since it was set up last week.
A Twitter account in the same name has also been created.
The site aims to "free Melissa and Michaella from a living hell in a Peruvian prison".
However, comments have already been posted on the site disputing the pair's version of events.
On Friday, Reid spent her 20th birthday in a Lima police cell and had an emotional reunion with father, William, 53. The former call-centre worker is said to have told her father: "They made me do it."
She told him that while she worked on the Mediterranean island of Ibiza she was introduced to a British man who eventually forced her into meeting Colombian gangsters, who put a gun to her head.
Reid told her father the gang forced her to fly to Peru, adding: "I wanted to tell the air hostesses or anyone in the airports. But the men said they would know if we had spoken to anyone, that they were watching all the time.
"It was a choice between doing what I was told and getting it over and done with and hopefully getting back to Spain, or trying to escape and being killed."
Reid also said she fears evidence in Peru has been contaminated by police because they did not wear gloves as they handled the food bags in which the drugs are said to have been stored.
Her father William said "of course" he believes his daughter is innocent, claiming she was in the "wrong place at the wrong time".
Both women may be held pre-charge for up to 30 days and could then spend up to three years in prison before a trial.