Energy firm Cuadrilla has said it is scaling back work at an exploration site in West Sussex on police advice.
The company has been drilling for oil near the village of Balcombe but has not ruled out using the controversial technique of fracking to release gas. Police believe environmental activists at the site are about to begin a campaign of civil disobedience. About 1,000 extra campaigners are expected to join existing protesters this weekend, according to police.
Exploration operations will be effectively at a standstill just two weeks after drilling got under way at Balcombe. The number of workers on the site has been reduced and large reinforced fences are being erected. Cuadrilla said in a statement: "After taking advice from Sussex Police, Cuadrilla is scaling back operations ahead of this weekend's No Dash For Gas event. BBC's John Moylan said Cuadrilla had put the site into lock-down mode "During this time, our main concern is the safety of our staff, Balcombe's residents and the protesters following threats of direct action against the exploration site. "We will resume full operations as soon as it is safe to do so." Cuadrilla is drilling a 3,000ft (900m) vertical well and a 2,500ft (750m) horizontal bore but said fracking for shale gas would need fresh permission.