The emergency services were alerted to an incident at Dovestones Reservoir, earlier on Tuesday, March 2nd.
When they arrived at the scene, the fire had gone out.
Initial thoughts were that a group of youths were responsible for starting it.
Police officers spoke with five people at the scene. They were issued with fines for breaching coronavirus lockdown rules.
Firefighters made the area safe and dampened down as a precuation.
GMP Saddleworth and Lees Facebook page read: "Earlier this evening Police and fire brigade received a report of youths starting a fire at Dovestones reservoir.
"On arrival the fire had been extinguished and fire brigade further doused the area with water for safety.
"Five adults were spoken to and issued with fines for breach of covid regulations."
There have been scores of visitors to the sites, despite lockdown restrictions, in recent months.
