At around 5.35pm, Police launched units including a helicopter, to Threipmuir Reservoir in the Pentlands following reports about concern for a person seen in the water.
The person’s condition is not yet known and emergency services are still at the scene.
Both the Scottish Fire and Rescue Service and the Scottish Ambulance Service are also at the scene.
Enquiries are ongoing and Police Scotland confirmed their investigation is still at an early stage.
A Police Scotland spokesperson said: “At around 5.35pm on Wednesday, July 14, police were called to Threipmuir Reservoir near Balerno following a concern for a person seen in the water.
"Emergency services remain at the scene and enquiries are ongoing.”
Both the Scottish Fire and Rescue Service and the Scottish Ambulance Service have been contacted for comment.