A senior fire officer has said it had been a "challenging weekend" after an industrial fire involving tonnes of rubber material and gas cylinders.
Fire crews were called to Enterprise Way, Derby, at 13:40 BST on Monday as blasts were heard across the city.
Heaps of rubber 'crumb', used in playgrounds and sports fields, were ablaze and plumes of thick black smoke could be seen across the city.
The fire happened as other crews were helping with moorland fires.
Up to six explosions were reported and Derbyshire Fire and Rescue Service sent about 50 firefighters on eight appliances to tackle the flames.
No-one is believed to have been hurt and an investigation is under way.
Station manager Adam Bleakman said the service had anticipated a busy Easter weekend: "We had plans in place, because of the dry spell and knowing there would be visitors to the Peak District.
"We've had a number of other incidents across the county but we have maintained fire cover during a challenging weekend for the service."
He confirmed the rubber was still being damped down on Tuesday morning.
The building itself, along with a neighbouring unit, is thought to have suffered cosmetic damage only.
St Mary's Wharf police station was evacuated for much of the afternoon due to the smoke and trains north out of the city were suspended.
People living nearby were told to keep windows and doors shut.
The Environment Agency said it had found contamination from the fire in the Derwent river and was using a boom to contain it.
Bill Worthington, operations director at Nova Sport, which runs the building, said he was "shocked" and estimated up to 40 tonnes of rubber material had been destroyed.