Teenage boy's body found in mountain creek

The older boy activated his personal locator beacon shortly before 6pm on Wednesday after the pair became separated.

A multi-agency response was triggered, with the 17-year-old boy winched from the Acacia Flats camping ground, about 36km from Mount Hay.

The search for the 16-year-old continued as rescue helicopters, paramedics and rescue squads scoured the wilderness.

His body was found in a creek in Blue Gum Forest at the Blue Mountains National Park about 1pm on Thursday.

"A post-mortem examination will be conducted in coming days to determine the cause of death, and a report will be prepared for the information of the coroner," NSW Police said.