LONDON, March 26 (Xinhua) -- A major incident has been declared after around 200 barrels of reservoir fluid leaked into Poole Harbour, in Southern England's Dorset on Sunday, local authorities have said.

"It is estimated that approximately 200 barrels of reservoir fluid has been released into the water column in Poole Harbour," said Poole Harbour Commissioners (PHC) in a statement.

Typically, there are five main types of reservoir fluids: black oil, volatile oil, condensate (retrograde gas), wet gas, and dry gas.

The PHC said the leak had come from the Wytch Farm facility, operated by hydrocarbons' producer Perenco. Wytch Farm is one of the largest onshore oil fields in Europe.

"PHC have activated their oil spill plan and are working with a number of organizations. A major incident has been declared, and a gold command unit has been established," it added.

Members of the public have been urged not to swim at Poole Harbour or the surrounding area until further notice.