Both Eliza and Henrietta are described as being white, slim build with long, brown hair.
Police said the side of Victoria Bridge in the Torry area, where they were last seen, contained many commercial and industrial units and searches are ongoing there.
It added it was urging businesses in and around the South Esplanade and Menzies Road area to review CCTV footage recorded in the early hours of Tuesday and dashcam footage.
Ch Insp Darren Bruce said: “We are continuing to speak to people who know Eliza and Henrietta and we urge anyone who has seen them or who has any information regarding their whereabouts to please contact 101 quoting incident number 0735 of Tuesday, 7 January, 2025.”