NEW YORK — Investigators in New York are trying to figure out what happened to two sisters who were found floating near an embankment of the Hudson River last Wednesday. Police say 23-year-old Rotana Farea and 16-year-old Tala Farea were similarly dressed and bound together at their ankles and waists with duct tape. For nearly a week, police sketches were the only leads authorities had.

"We are out to get justice for those two girls and to find out exactly what happened what led them to be recovered in the water," said NYPD Chief of Detectives Dermot Shea.

At a briefing Wednesday, police said the medical examiner determined the sisters were alive when they entered the water. However, their cause of death has not been determined.

The sisters lived in Fairfax, Virginia. According to police, they were last seen there in late September, but what happened after that remains a mystery.

"At this point in time it has still has not been determined a homicide," said Shea.

Sisters Tala Farea, 16, and Rotana Farea, 22, were found dead in New York's Hudson River. NYPD

A source with the New York Police Department tells CBS News the mother, who lives in Virginia, told police she received a call from the Saudi government in October telling the family they all had to go back to Saudi Arabia because the sisters had applied for immigration asylum.

Police are still investigating what exactly happened, but they are calling the deaths suspicious. The investigation has been hampered because there is virtually no digital footprint. The sisters didn't have a registered phone or any presence on social media.