A company in Thetford was lucky to escape serious damage after arsonists poured petrol through a letter box and ignited it by posting a lit newspaper.

Guardline Technology's building on Brunel Way suffered fire and smoke damage to its front foyer after it was attacked between 1.30am and 1.47am on January 14.

Norfolk police said the damage could have been much worse if a second set of closed doors had not prevented the fire from spreading further into the premises.

Investigating officer Det Con Mark Sneath, from Thetford CID, said: 'The business unit had double doors in the foyer separating it from the rest of the building. Had they not been there the fire would not have been so contained and could easily have spread further.

'We take these incidents very seriously and I would appeal to anyone who may have seen suspicious people or vehicles in the area to come forward.'

Guardline, which manufactures hygiene clothing for clean rooms and employs about 60 people, has been at the site for about 10 years.

Managing director Ray Wheeler said: 'We were lucky the fire burnt out as quickly as it did, and that there is an inner door and thankfully there was not a lot of damage. We have got to take it as a serious attack rather than just vandalism.'

Mr Wheeler the flames had set off the building's burglar alarm, and that the company had now put extra security in place at the premises.

The firm's fortunate escape prompted renewed warnings from Norfolk fire officers and advice on how businesses could protect themselves from similar attacks.

Arson reduction officer Dave Farrow said there were several, common-sense prevention measures which businesses could take to reduce their risk.

They included installing metal letter-boxes which hold mail in a flameproof container, locking waste bins and clearing flammable waste from outside the building.

He said smoke detectors should always be fitted, while companies which felt particularly vulnerable could also consider staff awareness training, access control, and the installation of CCTV.

'Everybody is different, so I would rather go an visit people to give true, site-specific advice,' he said. 'But if you can reduce the risks you can make it much less likely you will be a target. It is common sense at the end of the day. The more difficult it is to commit arson, the less likely someone is to go and do it.'

?Anyone with information about the Thetford arson should contact DC Sneath on 0845 456 4567 or Crimestoppers on 0800 555 111.

?For site-specific anti-arson advice, contact Mr Farrow on david.farrow@fire.norfolk.gov.uk.