"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.
Rotana was enrolled at George Mason University, but left in the spring. A George Mason spokesman called the news of her death "tragic," and said the university was cooperating with police.
Police said the sisters left their family home and were placed in a shelter after an earlier disappearance, in December 2017.
They were reported missing again Aug. 24.
"At this point in time it has still has not been determined a homicide," said Shea.
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.
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