Fire crews had to return to a derelict Wigan mill which suffered heavy damage in a huge recent blaze for another major operation.
Firefighters were called to the landmark site on Leyland Mill Lane twice on Saturday after large amounts of smoke were spotted rising from the wrecked building.
Crews initially went to the Marylebone site at around 9am but were called back at about 2pm as the situation was getting worse.
Firefighters then spent almost three hours pouring water onto the derelict building to try to contain the flames and smoke, with four engines from the borough being supported by an aerial platform which came all the way from Manchester.
The fire service has now explained it is far too dangerous to try to get into the building and completely put out the fire, which is located underneath one of the floors.
People who walk past the mill and see the area is still smoking are therefore being asked not to automatically call the emergency services, although it has been stressed crews will immediately attend if it seems the fire is picking up strength again.
Firefighters have also urged residents to stay away from the building.
Watch manager Carl Gleaves from Wigan fire station said: "We went this morning and decided we would review it at about 4pm, but we were called back before that and it had got worse.
"It is not worth the risk trying to get into the building to tackle the fire fully.
"We've been putting copious amounts of water on it from the top, and the aerial platform helped us to get enough height to do that safely.
"But it's like a candle being lit underneath a bowl. If you pour water onto the bowl you are never going to extinguish the candle.
"We're trying to eliminate the hotspots as best we can.
"Our message to the public is if you see small wisps of smoke from the mill don't call 999 for that. However, if it is clearly taking hold and starting to develop then call us and we will come down.
"We also advise that absolutely nobody should go anywhere near the building. It is extremely insecure and it would be an awful set of circumstances if someone were to go in there and it collapsed or worse.
"People should steer clear until it is safely dealt with."
Mr Gleaves said talks are under way with Wigan Council and the fire service is recommending the local authority get the building demolished as soon as possible.
Fire initially took hold at the former Potter's Herbals factory on the evening of Thursday May 9.