Those considering re-washing pre-packaged lettuce at home to avoid an outbreak of salmonella poisoning might be doing more harm than good, an industry source has warned.

Fifty-four people in Victoria have been diagnosed with having a rare strain of the bacteria and two were hospitalised after eating leafy greens linked to Tripod Farmers, based in Bacchus Marsh, west of Melbourne.

The company has withdrawn 30 products from supermarket shelves and is investigating the salmonella source.

The outbreak is believed to be linked to a fertiliser sourced from chickens that was used to grow the lettuce.

Tripod Farmers recalls products from: Coles and Bi-Lo supermarkets in Victoria, New South Wales, South Australia, Northern Territory and the ACT

Coles and Bi-Lo supermarkets in Victoria, New South Wales, South Australia, Northern Territory and the ACT Woolworths in the ACT, Victoria and NSW

Woolworths in the ACT, Victoria and NSW Other trade outlets in NSW, Queensland, Victoria, South Australia, Northern Territory and the ACT

Other trade outlets in NSW, Queensland, Victoria, South Australia, Northern Territory and the ACT No salad products recalled in Tasmania, Western Australia

Richard Bennett, from Fresh Produce Marketing Australia New Zealand, said washing lettuce at home exposed it to harmful bacteria and cross contamination in the kitchen.

"By washing them ourselves, we actually expose something like leafy vegetables to contamination in our kitchen — from the bacteria in our sinks or cutting boards or from raw meat," he said.

Mr Bennett said it was impossible to replicate the thorough cleaning processes conducted in packaging facilities, in household kitchens.

"In the packing facility, where the fresh cuts are washed, sanitised and packaged, they go through an agitation rinse and a number of other washes to remove debris and pathogens, and I don't believe, in the kitchen, we can do any better than that," he said.

"Our sophisticated supply chain, temperature management, and the gas that's inside packages are designed to reduce to opportunity for containments to prosper."

'Most outbreaks aren't traced back to a source'

Eight cases of salmonella poisoning are being investigated in Queensland for links to Tripod Farmers, according to health protection executive director for Queensland Health Sophie Dwyer.

She said the type of salmonella identified in Queensland was rarely seen, which would have indicated to authorities that there could be an outbreak.

Mr Bennett said incorrectly identifying the root of an outbreak was worse than not identifying it at all.

But, in many cases the cause could not be traced back to a source.

"So it's good that they have been traced back to a source and a recall has been undertaken swiftly and all the contaminated product is off the shelves," Mr Bennett said.

Mr Bennett said identifying the wrong source could leave people vulnerable to the outbreak and impact the wrong industries.

In 2011, an outbreak of E coli in Germany was initially blamed on cucumbers imported from Spain.

Later, it was discovered that the source of the outbreak, which caused bloody diarrhoea, came from bean sprouts grown at an organic farm in Germany.

The false allegations cost Spanish exporters $US200 million per week.

The source of the latest outbreak has been confirmed and local agriculture has already taken a hit.

Moorabool Shire Deputy Mayor Paul Tatchell said he hoped the issue would be resolved quickly.

"The drought conditions along with the recent fires have put Moorabool's agriculture under enormous stress, and it's obviously having a significant impact on the local economy," he said.

"Issues like this only add to the fire and we hope it can be resolved very very quickly."