Thousands of litres of kerosene have polluted the River Don in Sheffield following a major fire at a waste management plant.
Officials from the Environment Agency are continuing to try to prevent the pollution spreading, following the fire at Frogson Waste Management on Douglas Road, Neepsend, at 4.30am on Saturday.
Around 40 firefighters spent several hours tackling the blaze, which involved two light goods vehicles and dozens of containers of mixed materials.
Among the containers were 6,000 litres of kerosene - much of which ran off into local drains.
Firefighters used clay mats to cover the drains to prevent the fuel spreading but were unable to stop all of the contamination.
The oil has contaminated water in the river around the Kelham Island area.
A spokesperson for the Environment Agency said: “We are investigating a pollution incident on the River Don following a fire in Sheffield over the weekend.
“The fire resulted in the water being contaminated with oil in the Kelham Island area.
“Our environment officers have been assessing the impact on the river, and working to prevent the pollution spreading.
“We have also been removing the pollution where possible.
“Contractors have been skimming the surface of the river, and water quality is now improving.
“So far we have received no reports that fish populations have been significantly affected, but we are continuing to monitor the situation, and we are checking the watercourse further upstream and downstream.”
He added: “If anyone sees any fish that appear to be dead or in distress, they can report the matter to our incident hotline on 0800 80 70 60.”
A spokesman for the fire service said preliminary investigations indicate the blaze started accidentally.
No-one from Frogson Waste Management was available to comment.