Officials say potentially toxic blue-green algae has been found in a Woodbury lake.

The Ramsey-Washington Watershed District confirmed the presence of the algae in Carver Lake on Friday, the city of Woodbury announced. The type of blue-green algae detected in the lake is known to produce toxins that can be harmful and even fatal to pets and humans.

Visitors to Carver Lake Beach and other lake users, including pet owners, are advised to avoid contact with the water.

Although most species of algae are necessary for aquatic health, blue-green algae, which is actually a photosynthetic bacteria, is bad news for lakes. These toxic blooms, which typically occur in late summer when water temperature are highest, have an unappealing appearance often compared to “pea soup, green paint or floating mats of scum,” according to the Minnesota Department of Health.

They can also give off a musty, sulfurous smell. However, whether a bloom is toxic or not cannot necessarily be determined by sight and smell alone.