Two people have died and several others have fallen ill following a listeria outbreak linked to rockmelons.
All those affected ate the fruit before becoming sick over a three-week period.
A deadly outbreak of listeriosis has had health authorities searching for the source for weeks.
One company stopped production on Friday and is now working closely with the NSW Food Authority to discover how a possible contamination occurred.
Health authorities say 10 elderly patients ate the fruit before six fell ill, including two deaths in New South Wales, one case in Victoria and three in Queensland.
"New South Wales Health has been investigating as rapidly as possible the notifications of these cases," NSW Health's Dr Vicky Sheppard said.
"It's an unusual number of listeriosis cases in a short period of time."
Listeriosis starts with flu-like symptoms including fever, chills, muscle aches, nausea, and sometimes diarrhoea - and it can take up to six weeks for symptoms to appear.
Most at risk are those aged over 70, pregnant women, or people with diabetes, cancer or a suppressed immune system.
The NSW Food Authority is advising those at risk to get rid of any rockmelon they have at home.
It says all affected rockmelons have been removed from stores and that all rockmelons currently on shelves are not linked to this outbreak.
The Australian Melon Association says it is "working closely with government food safety investigators... and will redouble our efforts to eliminate foodborne illness".
For those at risk, authorities have emphasised a general warning about rockmelon and other foods.
"This includes pre-cut fruit, pre-bagged salads and pre-made salads, cold chicken, deli meats, raw seafood and sprouted products," Dr Sheppard said.
There has been a total of 15 listeriosis cases reported in New South Wales already this year.
The possible source of those cases is still being investigated. While that happens, officials are keen to remind those at risk to avoid those foods.
Both Coles and Woolworths told 7 News they have already taken rockmelons off the shelves, and anyone who bought them can get a full refund.