People living in a small village in Cornwall say they are suffering from swollen eyes, soare throats and headaches amid a potent oil smell in the streets.
South West Water has started an investigation following reports of an oil spill in Cawsand.
The water firm says its staff found oil had entered the sewer from an "external source" and a tanker has been deployed to remove it and take it to a waste disposal site.
Cawsand resident, Ghilly McDermott, said a lot of people in the village have been able to smell the oil, which has been so strong it has caused sore throats amongst residents.
She said at first she thought the smell was coming from the toilet in her house, but after speaking with South West Water realised it was coming from the sewer system outside.
She said: "At first when we went outside towards the square it was really bad. Lots of people in the village have said they've had swollen eyes and sore throats from it.
"Other people have had the same thing for several days and everybody has got really swollen eyes, you know, they've really been affected by it."
A South West Water spokesperson said: "Following reports of a potential oil spill within the sewer network in Cawsand last weekend, we investigated and discovered oil had entered the sewer from an external source.
“We deployed a tanker to remove the oil and dispose of it at a local waste disposal site to ensure there was no impact to the environment.
“We are carrying out further investigations on the network and will look to remove any oil we may discover.
“We have spoken to the customer to advise them of the situation.”