The Pennsylvania Department of Health on Friday confirmed the state’s first death related to vaping.

The spate of severe lung illnesses related to vaping began in March and the number of people sickened has since surpassed 1,000, with cases being reported in almost every state. At least 18 people have died, according to the U.S. Centers for Disease Control and Prevention.

New Jersey and Delaware also announced deaths related to vaping this week.

“What we are seeing is truly a public health emergency in Pennsylvania,” Secretary of Health Rachel Levine said during a news conference Friday.

Pennsylvania has reported nine confirmed cases of vaping-related lung illness and a dozen probable cases. The state Health Department is investigating an additional 63 cases.

Nationally, most patients had a history of vaping cannabis products, though federal investigators have yet to identify a specific product or ingredient to link all the cases. Some patients reported using only nicotine vaping products.

“We do not really know what is causing these serious, and even life-threatening — even fatal — illnesses,” Levine said. “I strongly urge anyone who is vaping illegally bought products, in particular illegally bought products including THC, to stop.”

The U.S. Food and Drug Administration reinforced its warning against using vaping products bought off the street, especially those containing THC, in a memo published Friday.

The CDC has received age and gender information for 889 of the 1,080 cases reported by states. Among those patients, nearly three-quarters who were sickened are male and more than 80% are under age 35.

By contrast, a higher proportion of deaths have been in women, the Washington Post reported. Patients who have died ranged in age from 27 to 71, with a median age of about 50.

Levine declined to offer any specifics about the person who died in Pennsylvania, including whether the case involved THC, to protect the privacy of the patient and family.

Diagnosing vaping-relating lung illness has been challenging for doctors because its symptoms are linked to many other common respiratory infections. Chest X-rays of patients with vaping-related lung illnesses often resemble those of pneumonia patients.

Symptoms of vaping-related lung illness include coughing, shortness of breath, chest pain, nausea, diarrhea, fatigue, and weight loss.

Vaping is often identified as the cause of the illness only once other more likely sources, such as a virus or infection, are ruled out.

E-cigarettes have been marketed as a safer alternative to cigarettes that can help smokers quit, but the long-term health effects of inhaling vaping products that may include nicotine and other chemicals are unknown.

And as the number of illnesses and deaths associated with vaping continues to rise — without any conclusions from investigators about what is making people sick — several states are tightening regulations on e-cigarettes, particularly among teens and young adults.

New Jersey took steps Thursday to ban flavored e-cigarettes, one of several actions recommended by a task force on vaping convened by Gov. Phil Murphy.

Murphy promised “swift action” on the task force’s recommendations, which also included tightening regulations on e-cigarette advertising and heftier penalties for illegal sales to minors. A ban on flavored e-cigarettes would require legislative action; a bill has already been proposed.

“From a public health perspective, nicotine, a chemical considered as addictive as heroin or cocaine, is highly addictive in any form,” New Jersey Department of Health acting Commissioner Judith Persichilli, who chaired the task force, said in a statement. “Appealing to young people through flavored e-cigarettes must be stopped.”