The two Irish and Scottish women arrested trying to depart Peru with 24 pounds of cocaine in their luggage spent Tuesday in medical checks and pre-processing ahead of an expected transfer to prison.
Prosecutors' office spokeswoman Karen Guardia says Michaella McCollum and Melissa Reid are expected to be formally charged by Wednesday afternoon and transferred to prison to await trial.
Since their Aug. 6 arrest at Lima's airport, the women's plight has received blanket coverage by British tabloids.
Their lawyers claim they were coerced by criminals who threatened them and their families.
A Peruvian police official says both women insisted on their innocence during questioning. He spoke on condition of anonymity.
Small-time smugglers who plead guilty in Peru usually receive six-year sentences and are free in about two years.