UNDATED -- Experts believe they have discovered toxic blue green algae at Keystone Lake, according to Nate Herring, public affairs specialist with the U.S. Army Corps of Engineers, Tulsa District.
"We have posted the lake with advisories that say 'Harmful algae present. Lake may be unsafe for people and pets,'" Herring said.
"We're discouraging people to not come into contact with the water, to not swim or wade in areas where the water is stagnant, foamy or discolored."
Scientists are taking samples from two fairly large BGA blooms, one near Mannford and one near Cleveland.
Test results won't be back until Monday, but Herring said the evidence is strong enough to post public safety warnings.
"Right now we're basically seeing perfect conditions for blooms," Herring said.
On Friday, the Army Corps of Engineers closed a swimming beach at Ft. Gibson lake due to BGA.
Park Rangers put up signs and locks to keep people out of the water. Official signage went up Friday afternoon warning swimmers that these parts aren't safe for diving in.
Ft. Gibson Park Ranger Josh Mathis said the bacteria are present year round, but with heat and dry weather the amount can rise to a dangerous level.
Blue green algae in mild cases can cause respiratory and stomach issues, even rashes. In more severe instances, people have seen nervous system and even kidney damage.
Young ones, elderly and pets are at the highest risk.
Over 4th of July weekend, Keystone Lake had increased traffic due to the BGA warnings at Grand Lake of the Cherokees.