The massive moorland fire in Saddleworth is now being investigated as arson.
Fire crews have spent more than a week tackling the blaze in extremely challenging weather conditions.
Police now say witnesses reported people lighting a bonfire at around 7.30pm on Sunday 24 June on the moors near the Stalybridge estate and officers are currently pursuing this as a possible line of enquiry.
Soldiers drafted in to help Greater Manchester firefighters tackle the Saddleworth Moor blaze will continue their temporary roles until the end of the week.
Around 100 troops from the Royal Regiment of Scotland have been involved in the operation in Tameside, including digging trenches in an effort to stop the moorland fires spreading.
On Wednesday there were 45 firefighters on the scene who were using specialist equipment and vehicles to extinguish the remaining pockets of fire, said GMFRS.
Firefighters are being supporting by two helicopters from United Utilities which are continuing to dampen down targeted areas.
GMFRS firefighters and others from around the country are also supporting colleagues from Lancashire to maintain control of a similar blaze at Winter Hill near Bolton which broke out when two moorland
fires either side of the hill merged on Saturday because of increased wind speed.
Lancashire Fire and Rescue Service said 20 crews were at Winter Hill on Wednesday as they continue to tackle smouldering areas.
A 22-year-old man arrested by Lancashire Police on suspicion of starting one of the Winter Hill fires has been released under investigation.
- Anyone with any information is asked to contact police on 0161 856 9353, alternatively call 101 or Crimestoppers anonymously on 0800 555 111.