A lorry delivering drilling equipment has had cables severed, according to protesters.
Roads into Balcombe have been blockaded as anti-fracking campaigners battle against an exploratory drill.
But Sussex Police have said cables were quickly mended and the demonstration is continuing peacefully - with no arrests so far.
This lunchtime the Department for Energy and Climate Change have granted energy company Cuadrilla a license for drilling to go ahead.
The Great Gas Gala started at 7am pledging to block the routes to the site south of the mid-Sussex village by parking on narrow pieces of road and using vigilante lollipop people to stop traffic.
The lorry is stranded behind the blockade but the driver is believed to have fixed the damaged cable.
Police are looking into the reported sabotage.
Around 100 are at the site to protest against fracking in Sussex.
Protester Jack Harris, of Lewes, said: "A police seargent is mediating and has asked if there's anything he can do to peacefully resolve the situation but we're not willing to go anywhere.
"Why is it the police's business to assist a fracking company?
"It's getting quite intense now. We've been told the police would use the 'force of the law' to move us if necessary."
A Sussex Police spokesman said: "There is a peaceful demonstration today, Thursday 25 July, outside the Cuadrilla site in London Road, Balcombe, involving some 100 people.
"A lorry trying to enter the site had its brake lines cut shortly after 8am, but a repair was quickly carried out without interference from any demonstrators.
"Demonstrators are currently blocking access for the lorry at the entrance to the site and we are in negotiation with them with a view to enabling the lorry to enter.
"There have been no arrests and no injuries. A small number of local officers are present.
"Sussex Police fully support the right to demonstrate peacefully and within the law.
"Our aim is to provide a safe and secure environment for protesters and residents, to minimise disruption to the community and to prevent crime and disorder.
"We have not 'threatened' them with arrest but in our discussions we are explaining the legal situation and making it clear that at some stage the entrance will need to be clear.
"Currently less than ten police officers and PCSOs are present."
A spokeswoman for Cuadrilla confirmed a lorry had been sabotaged and said vehicles on their way to the site this morning have turned around. She said no more deliveries are expected today.
Consent granted for Balcombe conventional appraisal well
This lunchtime (July 25) the Department of Energy and Climate Change gave Cuadrilla consent to drill a "conventional appraisal well".
A statement said: "The target prospect is oil located in micrite, a type of limestone within the Kimmeridge shale formation.
"DECC and the Health and Safety Executive have scrutinised Cuadrilla’s plans and the company has received the environmental permits required for this type of conventional drilling from the Environment Agency.
"The company does not have consent to use hydraulic fracturing.
"If Cuadrilla decides in the future it wishes to frack or to conduct further tests in Balcombe, the company would need to apply for further permissions, including consent from DECC."
Yesterday (July 24) Cuadrilla got a permit to drill an exploratory borehole in the search for oil and gas reserves from the Environment Agency.
But residents and activists fear it could pave the way for the company - the first to frack for shale gas in the UK - to use the fracking technique on the site.
The technique injects fliud into the ground at high pressure to fracture shale rocks and release natural gas trapped inside.
The Environment Agency has attempted to reassure people that the current permit does not allow the company to carry out fracking - and Cuadrilla has said it currently has no plans to frack the site.
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