A block of flats and offices that was hit by a fierce blaze is “not habitable”, according to fire chiefs.

Eastern Daily Press: Fire crews tackle the blaze in Fishergate in Norwich. Picture: Simon ParkinFire crews tackle the blaze in Fishergate in Norwich. Picture: Simon Parkin (Image: Archant)

The cause of the fire that spread through the upper floors of a building in Norwich is now being investigated by the fire service.

Nine crews were called to the building in Fishergate just before 2pm on bank holiday Monday after flames and a large plume of smoke could be seen coming from the roof.

In total, 25 Norfolk Fire and Rescue appliances from across the city and beyond were directed to the scene to help get the fire under control.

No-one was injured in the incident, with a fire service spokesperson confirming that all residents were “out and accounted for”.

Eastern Daily Press: Fire crews tackle the blaze in Fishergate in Norwich. Picture: Simon ParkinFire crews tackle the blaze in Fishergate in Norwich. Picture: Simon Parkin (Image: Archant)

Firefighters used the aerial ladder platform, main and hosereel jets to put out the blaze, while also wearing breathing apparatus to protect them from the thick smoke.

They later used a thermal imaging camera to check for hot spots, before they received the stop message five minutes before 8pm.

Emyr Gough, from Norfolk Fire and Rescue, told the BBC that the extent of the damage meant that it was unlikely anyone would be able to move back into the building straight away.

“Certainly in the roof the damage is substantial, and I would probably suggest at this time that the building is not habitable.

Eastern Daily Press: Crowds watching the fire in Fishergate in Norwich. Picture: Simon ParkinCrowds watching the fire in Fishergate in Norwich. Picture: Simon Parkin (Image: Archant)

He also said that firefighters had worked “incredibly hard” to put out the blaze after being faced with a “substantial and developing fire on the roof of the building”.

With the smoke visible from across the city, onlookers lined the bank of the nearby River Wensum to watch as the afternoon’s events unfolded.

Tom Duncan, an eyewitness, said: “We saw lots of smoke and heard lots of sirens, then as we came around the corner we could see the flames shooting up into the air.

“It had really taken hold and was well alight. They seemed to quickly get it under control but it has taken them some time to completely put it out. I just hope whoever lives there is okay.”

Another bystander, Sarah Chapman, said: “We have seen some people leaving but I just hope no-one has been hurt. The building has been really badly damaged so people may have lost everything.”