It's believed a man with a "significant tail" of shedding the virus who has returned to the area is the likely source of the find.

But the Department of Health and Human Services has put out a testing call for locals and visitors after revealing viral fragments were found in a treatment plant sample taken on November 23.

The local testing blitz comes as Victoria's streak of no new virus cases extended to 34 days on Thursday, with 10,094 tests in the previous 24 hours.

Testing commander Jeroen Weimar said Barwon Health identified the former case in Colac and he wasn't infectious en route.

"We know they've moved back into the area and they're likely to be a significant source of that positive that we saw last night," he said on Wednesday.

Despite the man's presence in Colac potentially explaining the positive sample, Mr Weimar said he was keen to continue to increase test numbers.

"I'm very pleased that we've made the connection to this individual," he said.

"Nevertheless, we know that Colac is a town of 15,000 people. If there's anybody in that town who's not feeling well, we still want them to come forward and get tested.

"We are doing some more work in Colac over the coming days looking at some of the major employment sites to make sure we've really run this one to ground."

Meanwhile, spectators will return to Flemington Racecourse for the first time in almost nine months on Saturday after the Victorian government ticked off plans for a small crowd.

The Victoria Racing Club has been granted permission to host 500 people at the Living Legends meeting.

Of the 500 tickets, 440 will be put aside for VRC members selected through a ballot and the rest designated as rotating places for runners' owners.

Premier Daniel Andrews said announcements would be made on Sunday about further easing of restrictions.

"That will be good news for many people right across Victoria," he said.

Australian Associated Press