Birds and fish have died after a mystery liquid coated a quarter-of-a-mile of a canal in the Black Country. The pollution was found in a stretch of the Wyrley and Essington Canal in Wednesfield, Wolverhampton.

The RSPCA has rescued two ducks, two swans and cygnets from the canal. Fishermen have also reported dead birds tangled in weeds and seeing fish floating. The liquid, which was initially thought to be diesel, is believed to be a mixture of oil washed from the roads and the canal’s algae breaking down. 

The Environment Agency is still carrying out tests on the substance, which covers the water between the Linthouse and Devil’s Elbow bridges.

Fisherman John Phipps, aged 65, said the area was home to several species of bird, including coots and moorhens, and said he had seen a dead coot tangled in the weeds.

The retired university worker from Spondon Road, Wednesfield, said today: “It is a very distressing sight. 

“I came to my usual spot to fish and couldn’t believe what I saw – I had to move quite a way up to escape it.

“I thought it was oil dumped from a boat or straight from a drum. 

“I hope it gets cleaned up as soon as possible. It’s a horrible scene.”

RSPCA spokeswoman Judith Haw said the two ducks were recovering at Stapeley Grange animal sanctuary in Nantwich. 

She said the swans were still receiving treatment as they were “badly contaminated” by the mixture.

She said: “RSPCA officers are visiting the scene every day to check for animals. 

“Anyone who spots a bird or animal in distress is asked to call our helpline.”

British Waterways spokeswoman Nicky Lister said original suspicions were that it was diesel. 

She said a team from the Environment Agency was now investigating.

Experts believe the recent heavy rain has washed oil from the roads into the canal and it has reacted with the algae.

Mr Phipps added: “Whatever it is, I hope it’s cleared up soon because it’s doing a lot of damage.”

Anyone who sees a distressed animal along the waterway is asked to contact the RSPCA on 0300 123 4999.