The NSW government approved controversial coal seam gas exploration at Gloucester before receiving proof that chemicals involved were safe for human health, throwing into doubt claims it is clamping down on the contentious industry.

It comes as protests at the site became heated this week, including allegations that a protester tried to hold the head of a security guard under water during a scuffle. Protesters described the claim as "exaggerated".

Police charged two protesters on Monday after they allegedly accessed the AGL site illegally. About 20 protesters reportedly blockaded the entrance to the site on Tuesday, but were kept out by a large police and private security guard presence.

AGL's Waukivory pilot project, south of Gloucester, has emerged as the latest front in community opposition to coal seam gas, following fierce protests around Narrabri and Lismore.

Fairfax Media has learned that the NSW Office of Coal Seam Gas signed off on the latest stage of the project before receiving lab test results confirming the chemicals to be used were safe to human health and the environment.

The AGL pilot involves the controversial process of hydraulic fracturing or "fracking", which forces gas to the surface by pumping water, sand and chemicals underground.

There are fears it can cause gas leaks, damage aquifers and pollute water with toxic chemicals.

Companies must demonstrate that all fracking additives comply with Australian drinking water guidelines, by having them tested by a certified laboratory.

The NSW government approved AGL's fracking work on August 6, despite officials not receiving the test results until more than two months later, on October 23.

A spokesman for Resources Minister Anthony Roberts said AGL was required to identify the chemicals to be used prior to approval being granted, but did not have to run tests on the chemicals before that date. The company was "compliant with its obligations", he said.

Groundswell Gloucester spokeswoman Jennifer O'Neill, whose group is opposed to the AGL project, said the timeline confirmed community fears about the approval process.

"It just feels dodgy from start to finish and we have to ask now, what else has been missed?" she said.

"It seems that both the Office of Coal Seam Gas and AGL are ... adopting a laissez-faire attitude to the health and welfare of the local community."

The group called for work to be suspended until AGL's application process was audited.

Greens MP Jeremy Buckingham said allowing AGL to start fracking before its chemicals were scientifically deemed compliant "defies common sense" and was at odds with community expectations.

AGL says the pilot will test the amount of gas produced from wells and provide data about the area's geology and groundwater.

A company spokeswoman said test results were supplied to authorities before fracking occurred and AGL had complied with government policy.

She said the results confirmed no banned substances were detected in its hydraulic fracturing fluids.

AGL reportedly required police escorts to move fracking equipment onto the site last week.

The spokeswoman said based on information from its private security team on Monday, "protesters were aggressive" and threw punches at guards who were attempting to prevent protesters from accessing the site.

"In one incident a security guard fell into the river and a protester allegedly tried to hold his head under water. A third security guard suffered a cut to his arm," she said.

Groundswell Gloucester member Ed Robinson described those reports as "exaggerated", adding "the guards have been particularly aggressive".

On Tuesday, Mr Robinson was building a camp that would hold 200 people, in anticipation that protesters will descend on the area.

"The community is dead against coal seam gas and very concerned about fracking, the chemicals used and the integrity of the wells," he said.

A spokesman for Mr Roberts said the minister met with concerned community members from Gloucester last week and authorities would "make regular inspections of the [AGL] fracking sites to ensure compliance".

The department "has and will continue to ensure a detailed level of transparency" around coal seam gas applications, he said.

In a report into the industry released last month, NSW Chief Scientist Mary O'Kane said the government should "establish a world-class regime" for coal seam gas extraction and ensure good communication about the industry's activities.

Laws should be supported by a transparent and effective compliance and reporting regime, she said.