Dog walkers have been warned to keep their dogs out of the water in Richmond Park following an oil spill coming from Beverley Brook.
Richmond Park said the Environment Agency and Thames Water “have put the appropriate control measures in place and continue to monitor the situation”.
The source of the leak is currently unknown but Thames Water said it believed that the spill was created by a third-party after they began investigating on Sunday morning.
“Our teams are currently establishing the source of pollution, which we believe was caused by a third-party.”
The spill is believed to have started in Pyl Brook, Morden Park before reach Beverley Brook, Thames Water engineers have created makeshift dams, using pads to wipe the oil from the surface of the water.
Thames Water is focusing on cleaning the sewers as a way of preventing any more oil flowing into the river whilst other protective measures are in place.
Richmond Park said there are no reports of any impact to the wildlife at present.