At its peak, more than 100 firefighters tackled the raging fire in the early hours of Easter Monday at the Tradpak Recycling premises on an industrial estate in the Armley area.
Plastic containers, with dregs of chemicals in the bottom, helped to fuel the huge blaze, which lit up the Leeds skyline.
Flames were seen rising high into the skies as clubbers left a nearby event at Canal Mills arts and music venue, which was evacuated.
Residents living nearby have been reassured by West Yorkshire Police, who confirmed smoke from the fire was ‘not toxic’ and said ‘swift work’ by firefighters and police officers meant there was no need to evacuate any nearby homes or even Armley Prison, which is about 300m from the scene.
Superintendent Mabs Hussain, of West Yorkshire Police, said: “We are continuing to assist our partners in the fire service in responding to what has been a major incident.
“We can confirm that the smoke from the fire is not toxic.”
Four neighbouring businesses premises were saved, thanks to rapid efforts by fire crews
Armley resident Gemma Rathbone was woken by loud explosions, saying: “We could see this massive, massive fire, all this smoke pouring out and the explosions were still going on so there were kind of like fireballs and we could see the flames jumping up. It was just huge”.
Supt Hussain added: “The substantial operation will continue for some time and police officers will work with fire investigators to examine the cause of the blaze when the situation has been made safe.
“I wish to thank residents for their understanding and also praise staff who worked extremely hard to bring a dangerous situation under control.”
Ian Dunkley, of West Yorkshire Fire and Rescue, said: “It’s been a really big job. We’ve had 100 firefighters on scene, 15 firefighting appliances, two aerial platforms and high volume pumps.
“The series of large explosions were LPG cylinders going off. Two premises succumbed to the fire but we managed to save four surrounding companies, which is a really good effort by the firefighters in the initial stages.
Residents were woken by loud explosions and high flames. Pat Hickey tweeted: ‘Got evacuated from canal mills. Leeds is on fire.’
Anja Swan, a student at Leeds Metropolitan University, said she heard explosions that sounded like thunder.
“I called my friend and they said they could see a fire so we had a walk down”, she said.
“We could see clouds of thick black smoke, just billowing out into the air. We could see this even from our house about half a mile or so away.
“There were fireballs shooting. It was really ferocious. Like Armageddon.
“There were quite a lot of people on the streets who had been evacuated from buildings.
“It’s a really huge fire. It was really quite scary. It was absolutely massive.”
West Yorkshire Fire and Rescue Service said the fire was not completely extinguished until the end of Monday.
Smoke could still be seen billowing last night.