Health advisory warning signs will be erected along the Katherine River on the weekend.
The NT Health Department said the signs were still being painted and constructed.
About 30 signs will begin to go up, mostly downstream of the High Level bridge from Saturday.
The warning advisory signs follow a Department of Defence PFAS chemical update in Katherine on Monday.
Katherine residents have been cautioned not to eat fish caught in the Katherine River and other homegrown produce.
Fish found below the Stuart Highway bridge have been found with high levels of PFAS and anglers have been warned to avoid eating the fish as a precaution.