The state government has announced it will impose a "hard border" with South Australia for 48 hours from Thursday night.
The border control measures will prevent travel between Victoria and SA, except for freight operators, those with medical or emergency reasons, those involved in urgent animal welfare, or people "authorised by law" such as child protection workers.
South Australia entered a six-day lockdown overnight after a COVID-19 outbreak, but reported no new infections on Thursday morning.
"From today, interstate truck drivers travelling through Victoria from South Australia will be offered extra testing at a site at Nhill on the Western Highway," the Victorian government said in a statement.
"Other testing sites are being activated at other major freight routes. Drivers can also be tested at more than 193 other sites across Victoria."
Meanwhile, traces of coronavirus have been found in wastewater at Portland and Benalla.
The state government urged the towns' residents and anyone who had visited there between November 15 and 17 and had any symptoms to get tested, and to isolate until they had a result.
The South Australian border restrictions will ease on Saturday night, when a permit system will be put in place.
The state government is yet to finalise the system, but it would allow people to cross the border if they were an emergency services worker, receiving or providing medical care, involved in farming or agriculture, or shopping for essential supplies
"Victorians have worked too hard and given too much to allow anything to put at risk our goal of reaching COVID-normal by Christmas," premier Daniel Andrews said.
"We'll do whatever it takes to keep Victorians safe. We know border communities have had an incredibly difficult year - and we don't take these decisions lightly.
"Our public health team will work closely with South Australia to monitor the outbreak and get the border back open as soon as it's safe to do so."
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