A person strolling through Riverside Park last Wednesday afternoon spotted something jarring on the riverbank and called the police.

There, below a small pier that juts out from the park at 68th Street, lay the bodies of two young women, bound together by duct tape at their waists and ankles. They had not been in the water long, the police said. Clad in similar black leggings and black jackets with fur trim, their bodies bore no obvious signs of trauma.

The police initially had trouble identifying the young women. Hints that they might be related surfaced a day after they were found when police sketches revealed striking similarities: the same curly dark hair, the same build, the same skin tone.

By Friday, detectives had learned the women were sisters from Saudi Arabia who lived in Fairfax, Va.