Prosecutors have rejected the guilty pleas of Dungannon woman Michaella McCollum Connolly and Scot Melissa Reid who attempted to smuggle £1.5 million worth of cocaine out of Peru.
Michaella McCollum Connolly (20) from Dungannon, Co Tyrone, and Melissa Reid (20) from Glasgow, pleaded guilty behind closed doors yesterday when they appeared before a judge in the port town of Callao, near the capital Lima.
But state prosecutors have asked for more information before accepting their admissions of guilt, which the women hope will bring their sentence down six years and eight months in prison.
A spokesman for the prosecutors' office in Callao said: "The two drug mules' guilty pleas have not been fully accepted, as far as the prosecutor is concerned, until they give more details.
"They will be asked to give another statement before the judge explaining where the drugs came from, who supplied them and why they said they had been forced to carry them by an armed gang."
The spokesman said a date was still to be determined for a new hearing, although following their guilty pleas court officials said the women would be sentenced on October 1.
McCollum and Reid initially claimed they were forced to board a flight from Lima to Spain with 24lbs of cocaine in food packets hidden inside their luggage when they were arrested last month.
By pleading guilty they sought to reduce the minimum sentence of eight years by a sixth, down to six years and eight months without the possibility of parole.
Reid's family has previously said they are working with the Foreign Office in the hope that the Peruvian authorities will allow her to serve part of her sentence in the UK.
Both women, who had been working on the Spanish party island of Ibiza this summer, have been held at the harsh Virgen de Fatima prison in Lima.
Court officials have said they may be transferred to the equally tough Santa Monica women's jail once they are sentenced.
Their guilty pleas came on the same day that the UN declared that Peru has now overtaken Colombia as the world's number one coca leaf producer.
According to a report by the United Nations Office on Drugs and Crime, coca plantations in Peru covered 60,400 hectares last year.
Peru's national prisons institute says that 90% of the 1,648 foreigners in the country's prisons are either sentenced or awaiting trial for drug trafficking.
It is still to be confirmed whether media will be able to attend the next hearing or the women's sentencing.