A gas valve at a fracking site in the Kimberley region was deliberately damaged, a preliminary investigation has found.
Footage taken by the anti-fracking movement Lock the Gate in January shows a hand-held gas metre reading high levels of methane near the valve at Buru Energy's Yulleroo 2, about 70km east of Broome.
Department of Mines and Petroleum executive director Jeff Haworth said an unauthorised person had entered the site and caused significant, deliberate damage to a valve on the well head.
Mr Haworth said investigators found the leak was very minor and gas could only be detected when the broken valve was manipulated.
He said filming the damaged valve would have also put lives at risk if the gas levels had been as high as claimed in the video.
Police are now trying to identify who damaged the valve.