The pollution was reported in the Sankey Valley Canal this yesterday, Tuesday.
It was spotted by concerned passers-by near to the Warrington Hospital entrance of Sankey Valley Park.
It was said to have a ‘diesel-like’ spell.
The Environment Agency has now told the Warrington Guardian that officers have attended the site and confirmed the presence of oil pollution.
They said they are now considering appropriate next steps.
A spokesperson said: “Our officers have attended the site and confirmed the presence of oil pollution. Samples have been taken for investigation, and we have located the source of the pollution.
“We are now considering appropriate next steps, including any appropriate enforcement action.
“We thank the public for reporting environmental incidents. Anyone can report pollution to the Environment Agency’s 24-hour incident hotline on 0800 807060.”