Toxic algae has returned to two lakes in Montgomery County, Maryland, and visitors, and especially dog owners, are being urged to take precautions.
Elevated levels of a toxin called microcystin that is produced by a type of blue-green algae have been found at Lake Needwood and Lake Frank, both located in Rock Creek Regional Park.
The toxin can cause liver damage in humans and pets if large quantities of contaminated water are ingested.
Swimming is not allowed at either lake, but people may boat or fish, which are being allowed to continue.
Montgomery Parks is asking people to avoid contact with the water. Some precautions to take include washing hands thoroughly before eating, drinking or smoking, if there has been water contact. And for fish caught at the lakes, make sure to only eat properly cooked muscle meat.
However, the biggest concern is for dogs.
Dog owners are urged to keep their pets on leash, as park rules require, and prevent them from drinking the water or coming in contact with it.
Microcystin was first found at Lake Needwood in 2009, and testing has been done regularly ever since.
When the toxin turns up, the park puts up signs to let visitors know.