The investigation is ongoing
A 20-year-old man was arrested on Friday morning on suspicion of arson with intent to endanger life in relation to the fire on Winter Hill.
Lancashire Police said the Wigan man was arrested by police investigating the moorland blaze near Bolton.
A force spokesperson said the investigation is continuing.
The Winter Hill fire was declared a major incident after two separate fires merged following accelerating wind conditions.
A 22-year-old man was arrested and later released under investigation last week on suspicion of starting one of those fires.
A police helicopter had previously spotted arsonists lighting new fires as firefighters combatted the blaze.
Tony Crook, from Lancashire Fire and Rescue Service, told Sky News at the time the incident was “absolutely heart-breaking and unbelievable.”
“Unbelievably, just the other side of the reservoir, there is a fire developing in that location,” Mr Crook said.
He said that as the helicopter flew over the moors it identified people “actually lighting fires.”
“Police are now attending that scene, to try to apprehend those arsonists. It absolutely astounds me.”
The UK has been in the grip of a heatwave, that’s actually affecting the entire planet, that could deliver the hottest day of the year today.