The Department of Agriculture and Water Resources told Reuters via e-mail that it was investigating whether any rock melons, also called cantaloupes, had been exported.
They include four Victorians and one Tasmanian.
A third person has died from listeria linked to contaminated rockmelon as the number of cases across Australia rises.
"All 15 cases are elderly people, and majority have significant underlying health conditions", NSW Health's communicable diseases director Dr Vicky Sheppeard said in a statement on Friday.
15 elderly victims have already been infected after consuming rock melon, also known as cantaloupe.
The New South Wales Food Authority said the company whose rock melons had been contaminated with listeria is an exporter of produce.
All 15 victims were elderly citizens, NSW Health said late on Friday.
Rockmelons have been withdrawn from supermarket shelves across Australia following the outbreak, which began in January. Its cases usually involve unpasteurised milk or dairy products, such as camembert and brie.
The ministry said in a statement yesterday that it had received a global notification in this regard and a follow-up of the issue, carried out with other entities concerned, revealed that limited quantities of the product were distributed in some outlets on Thursday, March 1.
The grower has ceased trading in melons and is now under investigation.
12 others are ill after an outbreak of listeria, and authorities are expecting more cases.
Of the three people who have died, two were from Sydney.
Listeria can be extremely serious and even life-threatening for people over the age of 70, pregnant women, and anyone suffering from diabetes, cancer or weakened immune systems.
Listeriosis begins with flu-like symptoms including chills, fever and muscle aches and can take up to six weeks to show symptoms.
The effects caused by Listeriosis can be deadly especially to elderly people.