Four farms within the Swan Hill district have now tested positive for anthrax.
Agriculture Victoria is working with landowners following the two latest positive test results which were confirmed this morning.
Anthrax was first identified at a property west of Swan Hill earlier this month, following the death of a number of sheep.
A second confirmed case was detected at a separate but related property last Friday.
This morning a further two properties returned positive results.
While this now brings the total number of confirmed positive test locations to four, Agriculture Victoria said it was important to note that these properties were "adjacent to the premises already identified on Friday."
Agriculture Victoria is responding with well established procedures to contain the disease, including vaccination of exposed and at-risk animals and disposal of carcasses of affected stock.
Each of the infected properties have been quarantined and movement of livestock is being investigated, including to other premises.
Agriculture Victoria said as the Incident Management Team was already in place, the response to these additional cases had been "swift and comprehensive".
Anthrax does occur in Victoria from time to time and it is not entirely unusual for the disease to emerge at this time of the year, with notable outbreaks in 1997 and 2007.
"Local farmers, veterinarians and Agriculture Victoria staff are working together and are well prepared to handle these biosecurity incidents," the spokesperson said.
"We urge farmers and those working with livestock to be vigilant for anthrax.
"Prompt reporting of suspected cases may potentially reduce the contamination of affected farms."
Any unexplained sudden deaths in livestock should be immediately reported to the 24-hour Emergency Animal Disease Watch Hotline on 1800 675 888, to local vets or to Agriculture Victoria animal health staff.
Agriculture Victoria staff will continue to be deployed until no further infected farms or infected livestock are detected.