'Drug mules' Michaella McCollum and Melissa Reid could face a six-month investigation if their guilty pleas are not accepted, the Peruvian prosecutor in charge of their case has warned.
Last week McCollum, from Dungannon, Co Tyrone, and co-accused Reid, from Glasgow, pleaded guilty to charges of drug smuggling.
But prosecutors are now demanding more information before accepting their admissions of guilt, which the women had hoped would reduce a potential eight-year prison sentence to six years and eight months.
Juan Mendoza spoke after the women, both 20, appeared before a judge at Sarita Colonia del Callao jail, in Callao, near Lima for a second time. He did not provide details of the private hearing but suggested the prosecutors were still not satisfied with their confessions.
Mr Mendoza, speaking to The Associated Press, would not discuss whether the women had given further explanation as to how they got the cocaine, or who gave them the substance.
McCollum and Reid initially claimed they were abducted, held at gunpoint and forced to board a flight from Lima to Spain with 24lb of cocaine in food packets concealed inside their luggage when they were arrested.
On Tuesday, an Irish priest visiting the women said they were in "brilliant" health and were "very very well" as they wait to be sentenced.
Father Maurice Foley said he found them sitting under a parasol in the jail yard drinking coffee whilst making phonecalls when he arrived last Saturday.
"I thought they were in great form actually," he said.
Fr Foley said he did not speak to the pair about their legal case. But he said that he took McCollum to one side during the visit and advised her that she should not expect to secure a sentence as low as one year. The priest said he expected a seven year sentence, which could be reduced at a later stage.