A heron has died after being covered in thick black oil two weeks after a massive spill polluted rivers in Morden Park and Richmond Park.

The oil spill is thought to have started in Pyl Brook in Lower Morden, which runs into Beverley Brook in New Malden.

It is believed to have been dumped in the water and was spotted by a dog walker on March 25.

The Environment Agency is still working to clear the waterways and is investigating its cause.

But locals have reported that a heron covered in oil was found dead on Saturday morning.

The bird was found near Malden golf course.

A local volunteer for London Wildlife Protection, Ruhee, said: “We were contacted by people from the the golf course, he had been visiting there for two years. He must have suffered, that is the really sad thing, he had been seen like that for a couple of days at least and people had been trying to catch him.”

Ruhee said instead of being grey and white, when the heron was spotted last week it was black and covered in thick oil.

The volunteer is concerned more wildlife could be impacted as there is still a lot of oil in the water. She added: “I went for a walk with a friend on Sunday along part of the Beverley Brook and we saw a big collection of oil, we reported it to the Environment Agency.

“The smell was awful. The problem is it is really difficult to get rid of everything, it is really thick and black and gets caught up in shrubs along the way so it can get logged for some time then move on.”

In the aftermath of the spill dog walkers on Wimbledon and Putney Commons and Richmond Park were warned against letting their dogs enter the water.

Pyl Brook is a small stream with two sources, a 5.3km main brook in Sutton Common that joins Beverley Brook in New Malden and a 3.9km East Pyl Brook that eventually joins the main Pyl east in Raynes Park

A spokesperson for the Environment Agency said: “We are investigating the pollution incident in the Beverley Brook.

"We continue to work with contractors to remove the oil, limiting potential impact to the environment and wildlife. 

“Our priority at this time is to respond to this incident and limit harm to the environment as much as possible.

"We are also collecting evidence to support our investigation into this unpermitted water discharge activity.”

The body asked the public to report any pollution they spot by phoning 0800 807060.