After the Caribbean beaches of Mexico were hit by an infestation of stinky, brown algae, it’s now Mississippi’s waters that have to deal with an unwelcome algae bloom.

A toxic overgrowth of blue-green algae along the Gulf Coast has caused Mississippi to close all of its 21 mainland beaches, the water being unsafe for pets and humans to swim in, reported Smithonian. People are also advised against eating seafood sourced from that area of the Gulf.

While beaches on Mississippi’s barrier islands remain open for now, they are being carefully monitored for signs of harmful algae.

The blue-green algae is comprised of a bacteria that produces toxins that can cause sickness such as skin, eye, nose, or throat irritation; abdominal pain; headaches; and vomiting, among others, according to the Centers for Disease Control and Prevention.

The phenomenon was caused by spring flooding of the Mississippi River after heavy rainfall. To alleviate the impact of the flooding, officials had opened the Bonnet Carre Spillway, which diverted water to the Gulf of Mexico. The problem, however, was that the floods washed millions of tons of fertilized topsoil into the river, so when that nutrient-rich water made it into the Gulf, it created an ideal environment for algae growth.

While holidaymakers can relax on the sand, they won’t be able to enjoy the waters until the bloom is over. According to The New York Times, beach closures have unsurprisingly hit the state’s tourism industry hard amid the Fourth of July holiday.