The incident occurred at the site earlier this month, when a group of six trespassers were spotted on by the security guard.

When they were asked to leave, they responded by throwing rocks at the guard, who was left with no other choice but to call police. The trespassers were then arrested.

Jemena, the company that leases the site, condemned their actions and said people should not attempt to enter the site.

"Jemena treats the security of all of its sites very seriously and condemns the vandalism and trespassing that has occurred at the Bathurst Gasworks site in the past," spokesperson Michael Pintabona said.

"We remind the community that this is a dangerous site and that they are placing themselves at risk if they illegally enter the site."

The incident comes at a time when Bathurst Regional Council is closely monitoring the management of the site, in part at the request of deputy mayor Bobby Bourke.

READ MORE: Old Bathurst Gasworks site: Deputy mayor grows more fed up, demands weekly updates

While he has been critical in the past, Cr Bourke praised Jemena last week after a positive meeting between the company and council.

"Jemena have done a very good job of cleaning up there now, all those fallen trees that were on the side there, and I have seen workers down in there cleaning everything out," he said.

He also listed a number of ways Jemena planned to improve security, saying it was a start, and now it was up to Crown Lands to get involved with the future of the site.

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In addition to having a steel fence around the site, Jemena has now installed closed-circuit television (CCTV), new signage and a gate locking system that will allow police to enter the site.

A contractor has been engaged to conduct daily site surveillance, while Jemena staff also visit regularly.

Mr Pintabona said the company still hopes to end its 20-year lease of the site early and is working with closely Crown Lands to do so.