South Hams District Council has issued more details and a warning, urging people to be careful and avoid contact with a poisonous plant.
The potentially deadly Hemlock Water Dropwort is thought to be the UK’s most dangerous plant.
Although the plant is not poisonous to the touch, it is highly poisonous if consumed.
Contact with the sap has also been known to cause a rash and blistering in some cases.
SHDC said they are "currently seeking advice from specialists" to help them decide what "next steps need to be taken" to manage the poisonous plant.
To alert the public, the council will be installing signs at locations where the plant has been found, such as Longmarsh, Steamer Quay, Vire Island and riverside paths north of Totnes Bridge and Brutus Bridge.
All parts of the plant are poisonous, and symptoms, if consumed can include; vomiting, seizures, paralysis, hallucinations and death.