The Environment Agency is investigating after diesel oil spilled into a river in Somerset.
Agency officials were at the scene earlier after the spill, which happened in the River Brue, near the New Clyce bridge at Highbridge on Friday evening.
A spokesman said the clean-up operation would take most of the day and many volunteers were needed to help.
The agency plans to close several sluice gates to contain the spill and to use a pump to suck up the oil.
An Environment Agency spokesman said the cause of the spill was not known.