The spill comes just a week after another spill in the same area

Teams from the RSPB, the RSPCA and the Environment Agency were at the site between Cobden Bridge and Woodmill Lane on Saturday.

The spill came just a week after another one in the same area in which two grebes died.

The Environment Agency said it was investigating the source of the pollution and would take action.

It said it believed the oil had leaked into the water from a nearby housing estate.

The oil is believed to have leaked from a nearby housing estate

Jim Baker, spokesman for the Environment Agency, said: "We don't know where it's come from but we suspect it's someone putting oil in the wrong drain outside their house or outside their premises."

Southern Water are trying to trace the slick back through the piping.

Spokesman Nev James said: "If it's a thick oil that has come down the system then there is a chance that we'll be able to find out exactly where it's come from.

"If that is a commercial premises then obviously we'll be keen to take action against those people."