Queensland police are leading an investigation into food contamination that now spans four states.

A six-centimetre piece of metal discovered in a packet of sausages bought from a Woolworths store in Adelaide's northern outskirts prompted the investigation last month, the Australian Broadcasting Corporation reported.

Queensland police say objects up to six centimetres long were also found in uncooked, pre-packaged meat and frozen products in four stores in New South Wales, Queensland and Western Australia recently.

No-one is believed to have been hurt by the objects as they are large enough that an injury is unlikely to occur.

The South Australian Health Department said no meat is being removed from stores as the contamination has not been limited to a single product or manufacturer.