A firm at the heart of a national fracking row has discovered oil at its exploratory drilling site.

Cuadrilla, which has been test drilling for shale gas at a site in Balcombe since August 2, announced the discovery of hydrocarbons and oil in its rock samples.

The controversial fracking process, which has prompted thousands of protesters tocampoutside the gates of the site since work began, involves blasting water and sand at high pressure deep underground to cause miniexplosions which release shale gas.

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Caudrilla said it would conduct further “flow tests” to ascertain how much shale gas could be sourced in the village, but said it would need further permission to do so.

The firm drilled a 3,000ft vertical well and a 2,500ft horizontal bore well in Balcombe – but will now start removing work equipment before its permission for the site runs out on Saturday.

Andrew Quarles, Cuadrilla’s exploration director, said findings so far had been “encouraging”.

Protests continued this week as activists blocked a road with a vanand a woman locked herself to it as vehicles started leaving the site.

Vanessa Vine, of anti-fracking group Frack Free Sussex, said: “We need to take a long, hard look at how we are feeding our seemingly insatiable collective addiction to fossil fuels in increasingly extreme ways and decide instead to invest in energy efficiency measures and safe, renewable energy procurement technologies that will give us both energy security and lasting employment.

“If this industry is given official sanction to continue any stage of its very dangerous drilling operations and production of toxic, radioactive waste at Balcombe – and thereby beyond – the people of Sussex must start asking what interests, exactly, are really behind this suicidal, illogical and very worrying scenario.”

A Caudrilla spokesman said: “We have encountered oil in the rock sampling but we need to flow test the well to assess what rate it would flow at.”