LONDON (AP) — The only company drilling for shale gas in Britain temporarily suspended fracking Friday after a mild earthquake.

Cuadrilla said it halted drilling for 18 hours after a tremor was detected at its site in Little Plumpton, northwest England.

The British Geological Survey recorded the 0.8-magitude quake just after 11:30 a.m. Friday. It followed several smaller tremors earlier in the week.

Under U.K. rules, any tremor over 0.5 is classed as a "red event" and sparks a temporary shutdown while monitoring continues.

Cuadrilla said the tiny tremor was "way below anything that would be felt at surface, much less cause any harm or damage."

Fracking in Britain was halted after two tremors in the same area led to legal challenges. It resumed on Oct. 15.

Environmental activists failed in early October in Britain's High Court to keep Cuadrilla's fracking from proceeding.

Hydraulic fracturing, or fracking, involves pumping water and chemicals at high pressure to fracture shale rock and release gas.