A 20-year-old Pearl Harbor-based sailor is under investigation for allegedly sexually assaulting an 18-year-old civilian Monday night.

Police described the woman as an acquaintance of the sailor. Jurisdiction of the case was turned over to the Naval Criminal Investigative Service since it occurred at Joint Base Pearl Harbor-Hickam.

The Navy said the woman was treated at the Kapiolani Medical Center after the 8:45 p.m. incident.

The Navy declined to release any other details of the alleged attack.