Swimmers are being warned to not enter the water at The Pond in Safety Bay.
Recent water quality tests have produced "elevated results", but the City of Rockingham has not revealed what was found in the tests.
The City has put up warning signs around the area which state swimming in the water may cause "ill effects to humans and animals".
"The signs will be removed once further water results show the water quality has returned to safe swimming levels," the City of Rockingham wrote on their Facebook.
Police issue 31,000 driving infringements in first month of new AI cameras
Works underway on Rockingham and Safety Bay High School redevelopments
New measles exposure sites revealed in Bunbury
Dawesville man charged after allegedly leaving his elderly Great Dane to suffer painful conditions
Good Samaritan sought by police after helping teen during robbery in Baldivis
Under-16s social media ban now in force
Desperate search continues for missing Bunbury FIFO worker
Passengers now able to use credit, debit cards to tag on and off WA's public transport
New floating jetty speeds up emergency response times for Marine Rescue Mandurah