Fire-fighters tackling a blaze at a Norwich factory are making good progress in their efforts to prevent it spreading to neighbouring buildings or to part of the plant where gases are kept.

By 5pm good progress was being made in firefighters' attempts to control the fierce blaze at the Broadland Hams factory on the Sweetbriar industrial estate in Norwich.

However, a fire service spokesman said relief crews were being arranged and it was likely the operation would continue into the night.

Fire chiefs said a controlled burn-out was unavoidable as the building was too dangerous to fight the fire from inside.

The Porter family who have run the factory since it was built in 1986 confirmed that nothing was likely to be salvageable.

However, they are already looking for alternative premises so they can supply their customers again in the near future.

Emotional staff from the plant, which employs about 25 people, were among the crowd who watched the blaze rapidly advance.

Thick black smoke was issuing from the factory when firefighters arrived at about 1.50pm. Staff had raised the alarm when they returned from lunch and smelled smoke.

Pumps from Earlham, Sprowston, Carrow, Hethersett, Wroxham, Long Stratton, Wymondham, Aylsham, and Attleborough plus the aerial ladder platform from Great Yarmouth were on scene and eyewitnesses said the fire could be seen for miles around.

Shortly after it started, eyewitness Louise Hall, who works at an office block in Burnett Road, said: 'We are looking at it through our window. It seems to be getting worse and there's thick black smoke coming out of it. The whole side of the building seems to be on fire, and it's bellowing out flames.'

Another witness, Arlene White, from the nearby Pentagon Control Systems building, said they were evacuated about half an hour after it broke out.

Everyone was evacuated safely but one member of staff suffered slight smoke inhalation.