Officers from the Department of Fire and Emergency Services were alerted to a chemical spill along Towie Street earlier this month which could have endangered the community.
The chemical in Deanmill was analysed and indicated to be organophosphorous pesticide, a product under the trade name Phorachem, which is toxic to humans.
Shire of Manjimup president Paul Omodei said drivers dealing with dangerous substances need to adherence to safety warnings and luckily no health concerns were raised.
"Read and abide by the safety instructions on the label and importantly store and transport chemicals appropriately,” Mr Omodei said.