BOULDER, Colo. (CBS4) -- The City of Boulder and Boulder County are warning people to cautious of algal blooms in lakes and ponds this summer. The algae, found in slow-moving bodies of water, can be harmful for people and pets.

Officials said algae has been observed at Wonderland Lake in north Boulder.

"If community members see algae in lakes and ponds, they should take extra precautions to avoid contact with the water," officials warned. Some algal blooms can contain cyanobacteria, which can produce toxins that are harmful to dogs and humans at elevated levels.

Cyanobacteria blooms may look like thick pea soup or spilled bluish-green paint on the water's surface and can also create a thick mat of foam along the shoreline, according to the Colorado Department of Public Health and Environment.

"In general, the long, stringy, bright green strands that appear either slimy or cottony, or are mustard yellow in color are not the harmful type of algae," experts explained..

Officials stated that warmer temperatures, stagnant water, and nitrogen and phosphorus loading from fertilized lawns and other sources can facilitate algae and cyanobacteria growth.

The City of Boulder and Boulder County do not test for cyanobacteria at lakes and ponds because the production of cyanotoxins can be highly variable – with harmful toxins detectable at one time but not detectable hours later.

Visitors and residents should keep children and pets out of the water in any areas where algae are observed.