A specific type of algae in a western Minnesota lake is making dogs sick — one of them later died — and conservation officials say that children are particularly at risk of falling ill.

Blue algae is suspected in the poisoning of two dogs last week as they swam in Red Rock Lake in Douglas County, according to the Sheriff’s Office.

One dog became “very ill,” while another died, the Sheriff’s Office said.

“It appears that … heavy rainfall runoff and warm, humid temperatures” contributed to the conditions being ripe for an early bloom of blue algae, the Sheriff’s Office said in a statement. The algae can be seen floating on the lake, giving off a blue-green hue.

Anyone spotting blue algae on a lake surface is “strongly encouraged to prevent animals and children from having any exposure with, inhaling or ingesting water suspected of being contaminated with blue algae,” the Sheriff’s Office statement continued.

Most often, human exposure to blue algae leads to skin irritation, nausea, and eye, nose and throat irritation. Deaths are rare because the unpleasant odor and appearance of blue algae tend to keep people out of the water.

Blue algae like this is blooming on a western Minnesota lake.

Last year, Brock Tatge’s dog, Copper, suddenly became very ill. Copper had been fetching his tennis ball from Prairie Lake in Sherburne County.

“We noticed that Copper went on shore, began vomiting and panting very hard, and just looked very sick,” Tatge said. “I carried him to my truck and brought him to the vet’s office.”

Copper died, and the veterinarian who examined him believes he became ill after ingesting toxins from blue algae.