The department is investigating the supply chain links between the three farms that had egg recalls in the past month.

John Barry, from Australian Eggs, said the first recall of Bridgewater Poultry in March involved hundreds of thousands of eggs. These eggs were distributed across four states and sold at major retailers.

"The two recalls since then have been smaller quantities," Mr Barry said. "Ash Sons involved eggs sold at independent grocers and was NSW only.

"The recall from Saturday (April 6) involving Southern Highlands Organic [which] was across NSW and Victoria and involved eggs sold at Woolworths, but the quantity is relatively small as organic eggs are a specialty product."

NSW DPI has increased surveillance and monitoring at poultry farms and has issued biosecurity directions to individual properties, including quarantine of premises to stop movement of eggs into the marketplace.

Salmonella can be spread between premises via egg transport, egg pallets, feed, rodents and the movement of people and vehicles on and off farm," a spokesperson from DPI said.

Southern Tablelands producers, Rodney Pope from Free Range Eggs in Goulburn, and Theresa Robinson from Bumnuts Australia in Gunning, have had to account for the traceability of their product to both the Food Authority and the DPI.

"[We were] asked what we do, and we just produce our own, we haven't been buying and selling from other farms so we are less risk," Mr Pope said.

Bumnuts Australia who keep studious records were asked to supply daily monitoring, and delivery records. "I have all those records," Mrs Robinson said, "It's pretty transparent."

Mr Pope said, that it is possibly too early to know what affect the full extent of the recall will have for his business.

"I don't know exactly to what extent it has affected those farms whether they've had layers culled or if it's just a temporary cessation of selling eggs," he said.

The NSW Health and the Food Authority are investigating an outbreak of Salmonella Enteritidis, which has affected a total of 167 NSW residents since the strain was first detected in May 2018.