A major incident was declared on March 27 after an oil leak from an onshore field in Dorset in the UK.
The UK Health Security Agency in the South West said members of the public should not swim in Poole Harbour or the surrounding area until further notice after 200 barrels of reservoir fluid - consisting of 85% water and 15% oil - leaked into the water.
The leak has come from the Wytch Farm facility in the Purbecks, which is one of the largest onshore oil fields in Europe.
The facility, taken over by Perenco in 2011, was previously operated by BP.
Perenco said there had been a "limited oil leak" at one of its well sites at Wytch Farm.
The oil and gas company said its "incident management team was activated immediately" and the "leak was stopped".
Perenco said it was working closely with the relevant authorities and that a clean-up operation was under way.
Franck Dy, Perenco's Wytch Farm general manager, said: "Any spill is an extremely serious matter and a full investigation will be launched to ascertain what happened in Poole Harbour. It is important to stress that the situation is under control.”
Fluid leak sparks health alert in Poole Harbour in the UK
