The mallards had to be chased around Flints Caravan Park in Thornton after a call from concerned neighbours.

A spillage at a nearby stream is believed to have caused the incident.

The ducks have been taken to a North West specialist unit where they will be cleaned up before being returned to the wild.

The Environment Agency has also been at the scene, collecting what is thought to be a lubricant-type solution.

An investigation has been launched by the agency.

None of the animals was seriously injured in the incident but RSPCA is treating it as serious.

A team of 13 officers from the charity attended the scene in Thornton on Friday morning and spent most of the weekend there.

It comes a year after 56 ducks were covered in diesel at the same site.

Chief Inspector Rob Malloy, from the RSPCA, said: "We were contacted by concerned residents at the caravan park about some of the ducks which seemed to be covered in some kind of lubricant.

"There is a stream which runs adjacent to the park and is home to several families of ducks.

"It seems something has leaked into the stream and has got into the ducks' feathers and when they groom themselves, it will eventually get into their bodies.

"We don't know yet whether the oily substance is dangerous but we are hopeful it won't be and that it does not effect the birds.

"It has been quite comical trying to get the ducks caught as we have had to chase them under the caravans before catching them in a net.

"Obviously, being wild they are naturally scared of intruders so we have had to go back to collect other ducks once bad light came into play."

All the ducks have been taken to RSPCA Stapely Grange Wildlife Centre near Nantwich, where a team of rehabilitation specialists worked overtime to clean them up.

The Environment Agency has confirmed it has launched a joint investigation into the spillage.

A spokesman said: "We have been tracking the stream to the source of the pollution and hope to have more details about what the substance is next week.

"We will be working with the RSPCA but are pleased not of the animals affected by the spillage have been seriously injured."