A 17-year-old boy was found dead in Upper Mystic Lake off Shannon Beach in Winchester Saturday night at 8 p.m., according to Massachusetts State Police. 

Luis Tejeda of Lynn died Saturday night while swimming in the lake with another family member, police said. The two swam 100 yards from the beach’s shore, which state police said is past the safe swim zone.

While swimming together, the family member soon noticed Tejeda was no longer visible, police said. Lifeguards were off duty by the time the family placed a call to 911 at 7 p.m.

State police said Tejeda’s body was found by Stoneham firefighters in about 6 feet of water nearby where he was last seen. Foul play is not suspected and the official cause of Tejeda’s death hasn’t been determined.