Protesters claimed this was because workers deemed the site too wet to carry out the works, but the government has blamed the protesters, who were standing at the gates into the site from 7am.

The government has confirmed the drilling works "are still planned to occur this week".

A passing motorist called police to the site after spotting the gathering of people with cars parked along the sides of Birralee Road, rather than due to a confrontation between protesters and contractors.

Senior Constable Thomas Moir said the protesters were "not causing obstructions" and the equipment had been moved away from the site because the "weather wasn't ideal".

Westbury Region Against the Prison president Linda Poulton, who was at the site, said they would have moved aside if asked, but they weren't asked.

"We're not blocking it, we're happy to move if asked to," she said.

"They went in, walked around the site then said they wouldn't progress it. They'd have to remove a lot of trees to get in there.

"They did a preliminary site inspection this morning, wouldn't you think they would have done that beforehand?"

It was the second time the drilling works - which would test the rock and soil composition of the site - had been delayed since they were originally planned to begin on October 5.

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The works plan for the site listed blue pincushion and handsome hooksedge as threatened flora, and grey goshawk, wedge-tailed eagle, green and gold frog, masked owl and Tasmanian devil as threatened flora present on the site, as a result of an assessment.

Machinery must remain on formed tracks, with disturbance to vegetation and soil "to be kept to a minimum".

A low-hanging branch crossed the main entrance area that would be likely to impede machinery, while an inspection of the main track indicated the presence of other trees that would likely require removal, but were yet to be removed.

A government spokesperson said it was the protesters, rather than wet conditions, that had impeded works.

"The works did not proceed as planned today because of a small number of protesters on site," the spokesperson said.

"There was no requirement for any environmental consultants to be on site today as all of the required permits had already been obtained.

"The amount of vegetation removed will be limited to the minimum required to undertake the work.

"This due diligence work is critical for the preparation of requisite planning approvals and will continue to be scheduled until all requisite drilling is completed."