ENVIRONMENT Agency officers are baffled by repeated oil pollution in Batley Beck.
The oil, which appears to be a kerosene type heating oil, white diesel or similar, is entering Batley Beck through a small watercourse that runs down Field Lane in Batley.
The watercourse is mainly in a tunnel so it has been impossible for officers to trace the source.
Dave Preston of the Agency said: "There are very few access points and with the beck running entirely underground, it's literally like trying to find a needle in a haystack.
"The type of oil it is suggests it is new and probably coming from a business that is using it for heating or to run an emergency generator.
"The leak might not be obvious, so we want all businesses to check their oil storage."
Agency officers on Monday found more oil than in previous weeks. It appeared as a thick film on top of the water.
The Environment Agency can be contacted on 0800 80 70 60.
