Emergency services spent several hours at the scene of an outhouse fire.
Firefighters were called at around 4.55am on Thursday to the incident at a property on Tyldesley Road in Atherton.
Crews wearing breathing apparatus used a door lock puller and hose reels to tackle the blaze.
They managed to prevent the flames spreading beyond the outhouse, which was behind a mid-terraced property.
They then used a large fan to clear all the smoke.
Greater Manchester Police (GMP) were called at around 5.20am as the crews thought the circumstances could be suspicious.
Emergency services are now working together to establish exactly what happened.
Three fire engines from Leigh, Atherton and Hindley attended the incident and were at the scene for three and a half hours.