With all Mississippi beaches closed due to blooms of toxic algae, officials are warning people against eating seafood and fish from the affected areas.

Twenty-one beaches in Mississippi are closed due to a Harmful Algal Bloom, or HAB. HABs occur when algae – simple plants that live in the sea and freshwater – grow out of control. The algae can produce toxins that can have harmful effects on people or wildlife.

The current bloom is caused by cyanobacteria, a blue-green algae, capable of producing the harmful toxins.

People can become ill if they come in contact with water contaminated with HABs. They can also become ill with symptoms including rashes, stomach cramps, nausea, diarrhea and vomiting if they eat fish or seafood from the affected areas.

“It is advised that you use caution and do not take fish, crabs, or shrimp from the areas affected by the bloom. Any marine life from the affected area should not be consumed even if it is cooked or frozen,” the Mississippi Department of Environmental Quality said.

Fish and seafood caught outside the algae-infected areas along the Mississippi coast are believed to be safe.

Officials said they are conducting daily water sampling in the affected areas.