The bodies of 16-year-old Tala Farea and 22-year-old Rotana Farea, of Fairfax, Virginia, were found around 2:30 p.m. Wednesday in the vicinity of 68th Street and Riverside Park.
Responding officers found the bodies laying on rocks near the river.
A missing child poster said the women were last seen on August 24, and a police source tells Eyewitness News the bodies were bound together with duct tape around their waists and feet so that they were facing each other.
Both were fully clothed, and there were no signs of trauma.
Sources believe the bodies washed ashore with the tide and stayed when the tide went out.
The Medical Examiner's Office will determine the cause of death, and the investigation is ongoing.
In recent days, the NYPD sent detectives to Virginia to help unravel the lives of the two sisters. At first, police suspected they died in a suicide pact and said there was no evidence of a crime. But that thinking may now be changing, and sources say police now have a better sense of where the two entered the water and how long they may have been in the water.
The NYPD is also asking for public's help in solving what happened to the women.
Anyone with information is urged to call CrimeStoppers 800-577-TIPS.