The city of Hamilton has put out a warning to residents to stay away from the water at Pier 4 Beach.

The city says toxic blue-green algae has been confirmed at the beach near Bay St. North and Leander Dr.

Blue-green algae are microscopic, plant-like organisms that occur naturally in ponds, rivers, lakes and streams and can be dangerous to humans and animals.

City officials are urging residents to “not come into contact with the water” in Hamilton Harbour.

People who do come into contact with water containing blue-green algae may experience skin irritation, rash, sore throat, sore red eyes, swollen lips, fever, nausea, diarrhea, and vomiting.

Public health says if you are exposed to the water, you should wash as soon as possible with clean water.