A reservoir, that's less than two miles southwest of Pierce, Nebraska is under a Health Alert Friday.
People visiting the Willow Creek Reservoir are being advised not to go into the water.
The state found harmful algal blooms, also known as "toxic blue-green algae" above the state required levels.
And, they're encouraging people not to come in contact with the water.
When these health alerts are issued, signs are posted to advise people to be careful.
But you can still boat and fish.
Swimming beaches are closed.
You are not supposed to come in contact with the water, especially if there's a chance you could accidentally swallow it.
While alerts like this don't happen all the time, officials say it's not uncommon at Willow Creek for this time of year.
That's because of what they call "high nutrient loading."
"They come from the watershed," said Jeff Schuckman, the northeast Nebraska fisheries manager for the Nebraska Game and Parks Commission. "It's an agricultural watershed and it has a very large watershed in relation to the size of the lake and that's a contributing factor also. So, it's got this big watershed and the runoff coming from that watershed gets concentrated in the lake itself."
There are different symptoms for people who come in contact with the toxic blue-green algae.
Some can get a rash, blisters, and even headaches and vomiting if swallowed.
There will be two samples taken over the next two weeks.
If the levels are below the state's health alert threshold, the alert will be lifted.