Speaking on Thursday, Western NSW Local Health District chief executive Scott McLachlan said: "We believe we've tracked that down to a location in Western Sydney that has the same strain of COVID-19 and biological markers".

"We do believe we've picked up the originating case, it was a couple that were in Western Sydney and came back into our region what was now over four weeks ago. We're closer to that original strain."

He added it was "Just a matter of time" until COVID came into the region and people shouldn't focus on the past.

"What we now know is there's so much broad spread of this Delta strain across all of our communities, with people infectious in all of our communities it's not so much about where it came from it's about what's happening today," he said.

"What we know is today there were nine people infectious in our communities in Dubbo, Orange and Brewarrina, yesterday there were more people than that infectious in our communities and the day before there were more than that.

"It's nice to look in the rear vision mirror but what we've got in front of us is a real challenge to stop the spread in Western NSW."

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When asked if the information gathered from this investigation would be used in the future to help prevent the spread of further outbreaks, he said they were always learning.

"There's certainly a lot of learnings about how we do things different in the future, potentially to slow the spread early on," he said.

Mr McLachlan would not say where in NSW the couple were from.