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May 23, 2017, 12:15 AM UTC / Updated May 23, 2017, 12:15 AM UTC

Gas station nacho cheese that sickened 10 people and killed one of them was contaminated with botulinum toxin, the California Department of Public Health (CDPH) confirmed Monday.

“The nacho cheese sauce was removed from sale on May 5. (The California Department of Public Health) believes there is no continuing risk to the public,” the agency said in a statement.

“While there are still unanswered questions about this outbreak, these tragic illnesses are important reminders to be vigilant about food safety,” said CDPH Director Dr. Karen Smith. “As we head into the summer barbecue season, both indoor and outdoor chefs need to be on guard against all foodborne illnesses.”

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Botulism is caused by toxic bacteria, usually Clostridium botulinum but sometimes Clostridium butyricum and Clostridium baratii.

It’s best known as the illness caused by home-canned foods but it’s also found in honey. Home-made potato salad served at an Ohio church picnic killed one person and sickened 29 in 2015.

Nachos and cheese Shutterstock

A big enough dose of the toxin can paralyze and kill people.

Symptoms of botulism include blurred vision, drooping eyelids, slurred speech and muscle weakness.

“Botulism can be treated with antitoxin and supportive care, often in an intensive care unit. Botulism is fatal in about 5 percent of cases,” the CDPH said.

The nacho cheese outbreak was traced to a Sacramento area service station. The San Francisco County coroner’s office said the person who died was a 37-year-old man.

Botulism can be a silent killer, the Centers for Disease Control and Prevention says.

"Home-canned foods could be contaminated but look, smell and taste normal," the CDC said.

"If there is any doubt about whether safe canning guidelines have been followed, do not eat the food. Home-canned food might be contaminated if the container is leaking, bulging, or swollen (or) the container looks damaged, cracked, or abnormal."