Melissa Reid, 19, and Michaella McCollum Connolly, 20, are being held in custody in Lima on suspicion of drug trafficking after they were stopped from boarding a flight to Madrid.
Peru’s national police said they found cocaine thought to be worth around £1.5m – hidden in food in the luggage of the two women.
In a recently released online video, Ms Reid is questioned by a police interviewer and is heard to say: “I was forced to take these bags in my luggage.”
When asked if she knew they contained drugs, the 19-year-old from Lenzie in East Dunbartonshire said: “I did not know that.”
Ms Reid and Ms McCollum Connolly both left home for separate holidays in Ibiza earlier this summer.
Last week, Ms McCollum Connolly was at the centre of a Facebook and online social media appeal after her family said they had not had any contact with her for 12 days. The first they heard was when she turned up in Peruvian police custody.
Ms Reid’s mother, Debra, told reporters she thought her daughter was in Ibiza with friends and had no idea she had travelled to Peru.
Ms Reid flew to Ibiza in June and had posted numerous pictures of herself with friends on the Spanish holiday island on her Facebook page. Her last post was on 21 July.
The women are said to be in custody in a police station in Lima. Foreigners arrested on suspicion of drug trafficking in Peru can remain in holding cells in the anti-drugs police headquarters for 15 days while officers investigate.
Suspects are then either charged or released. If they are charged, they will be transferred to prison to await a court hearing.
Lead investigator Major Manuel Siclla told the Scottish Sun: “They are OK, but are obviously worried about their families and what the future holds for them.
“Like anyone else involved in drug smuggling, they will be tried and face long prison sentences if convicted.
“We take this problem very seriously here in Peru and courts are very strict about the enforcement of the law.”
The Foreign Office in London confirmed it was helping a British national. The Irish embassy in Mexico City is also helping Ms McCollum Connolly and her family.
It is understood the pair are being held separately in maximum-security holding cells.
A guard in Lima told the Daily Mirror that they had refused to eat or drink, and they were “terrified and emotional”.
Michael Russell, a retired consul general in Lima, told the paper: “The jails are pretty dour and horrible. It’s all a matter of money. You have to buy your space and food.
“If you don’t have money, you suffer quite a lot.”
He said the pair, if found guilty, could be sent to Lima’s notorious Santa Monica de Chorrillos women’s prison