The girls were found behind the Fairfield Townhouses at Holtsville at 2 Victorian Court in Holtsville on Saturday, Sept. 7, the Suffolk County Police Department said.
A family member called 911 around 3:15 p.m. to report the girls missing. Police found their bodies in the pond a few minutes after they arrived at the scene.
Their identities have not yet been released.
Paramedics took the children to Stony Brook University Hospital, where doctors pronounced them dead.
Suffolk County Police detectives ask anyone with information on the incident to contact the detectives at 631-852-6392.
This is a developing story. Check back to Daily Voice for updates.
Click here to follow Daily Voice Port Jefferson and receive free news updates.