A blaze on Saddleworth Moor which fire crews have been fighting for more than a week is being treated as arson.
Police say witnesses reported that people were lighting a bonfire on the moorland above Stalybridge, Greater Manchester, on the early evening of Sunday June 24 - about 50 minutes before the first emergency call to raise the alarm.
The fire on land at Buckton Vale, east of Manchester, later led two days later to the evacuation of dozens of homes in the village of Carrbrook as flames threatened to engulf properties and continued to spread as fire crews from across the country, with the assistance of the Army, successfully battled to keep the area safe.
On Wednesday with the fire still burning, although under control, Greater Manchester Police said the bonfire sighting was being pursued as a possible line of inquiry.
Chief Superintendent Neil Evans said: "The moorland fire is now being investigated as arson following information from local witnesses and initial inquiries.
"The scale of this fire is exceptional and we are treating it with the utmost seriousness.
"That said, we are under no illusion that solid evidence as to where the fire started and what was the cause will not be easy to establish."