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COLORADO SPRINGS, Colo. — The city of Colorado Springs closed one of its lakes due to concerns over toxic algae.

The “blue-green” algae is a naturally occurring event that popped up in Prospect Lake at Memorial Park.

“We had a good chunk of fish die off because of it,” said Erik Rodriguez, an environmental, health and safety specialist with the city of Colorado Springs.

Rodriguez said the city had to pick up about 500 fish from the lake Monday morning.

“Blue-green algae releases a toxin that is toxic to people and animals,” he said.

The major concerns revolve around kids and pets.

“Pets ingest it after they go swimming. It gets on their fur. And kids ingest it from just drinking the water,” Rodriguez said.

Pets can die within hours of consuming the algae. Kids can get sick and experience symptoms including a headache, diarrhea, weakness and liver damage.

The blue-green algae is easy to identify. It basically looks like a layer of blue-green film going along the shoreline of a beach.

“And then it will start to bloom out into the lake,” Rodriguez said.

If you or your pet comes into contact with the algae, you’re urged to call a doctor or a veterinarian.