Firefighters are still on the scene of a blaze that ripped through a business in an industrial estate.
After staying throughout the night a team from Wroxham has been dispatched to monitor the Power Tool Services unit in Rackheath Industrial Estate, Norwich.
Yesterday, King's Lynn station manager Mac Mcleod, at the scene in Earl Road, said the cause was a mystery.
He added: 'The initial structure collapsed on itself. The property has been completely destroyed. The adjoining property next to it has been saved.'
Mr Mcleod said nobody had been able to get into the building because it was not safe, with the fire burning underneath the burnt objects above.
At least six appliances plus specialist appliances tackled the fire and one police car attended.
As the blaze raged, people living nearby were urged to close their doors and windows, while others were told to avoid the industrial estate.
Businesses on other parts of the estate remained open, although Norfolk police evacuated people from nearby buildings including the snooker club.
Peter Rowe, group manager and incident commander, said: 'At 9am we received a call from the owner to report a fire in his industrial unit.
'We arrived at the scene and saw a well-established fire. Because of the contents of the building we are staying defensive.
'Our plan is to protect the adjoining buildings. Very serious damage has been done. A lot will be gone or damaged.
'We are doing our best to stop it spreading to adjoining buildings.'
The shocked owner did not want to speak in detail about what had happened but said he was inside and got out to call the emergency services.
One worker said he had seen five fire engines on his way into work. He said he could see smoke billowing up, but no flames.
A local business owner who rents a number of local units said he had received a call about the fire and arrived to see the smoke.
No-one has been hurt.
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