Residents in South Norfolk and Breckland are being urged to be vigilant following reports of rogue traders selling gravel.
Police have received reports of the material being offered to people with the trader claiming it is left over from a nearby job.
The gravel is offered at a cheap price, which increases once the product is accepted and laid.
Det Sgt Pete Jessop, of Norfolk police's Operation RADAR team, said: 'No legitimate company goes door to door offering gravel in this way. Our advice is only to deal with reputable companies which you have hired yourself and have obtained a written quote from.'
People should always ask for ID from salesmen, should not feel pressured into signing or agreeing anything on the spot and should take any paperwork away to read.
Anyone concerned about this issue should contact Norfolk police on 101 or Consumer Direct on 08454 04 05 06.
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