San Francisco’s Juul and other e-cigarette makers have 60 days to tell federal regulators how they plan to reduce sales to teens — or face having their products taken off the market, the U.S. Food and Drug Administration said Wednesday.

The move is part of a crackdown on e-cigarette youth sales by FDA Commissioner Scott Gottlieb. The agency over the summer issued 1,300 warning letters and fines to retailers that illegally sold Juul and other e-cigarette products to minors.

“We see clear signs that youth use of electronic cigarettes has reached an epidemic proportion, and we must adjust certain aspects of our comprehensive strategy to stem this clear and present danger,” Gottlieb said in a statement.

Juul, one of five major e-cigarette manufacturers named in the FDA action, is estimated to have at least 65 percent of the market for e-cigarettes. The company sells devices resembling a thumb drive that contain flavored nicotine. The growing popularity of the vaporizers — which come in mango, mint, cucumber and other flavors — is prompting concerns about nicotine addiction among a new generation of young people. A Juul “starter pack,” which includes the device and a four-pack of pods, sells for $50. Additional, refill pods cost $16 for a pack of four, Each pod lasts for about 200 hits and has roughly the same amount of nicotine as a pack of cigarettes.

In 2016, about 11 percent of high school students reported using e-cigarettes in the past 30 days — up from 1.5 percent in 2011, according to the Centers for Disease Control and Prevention.

In a statement, Juul said it “will work proactively with the FDA in response to its request,” but it did not specify steps it may take to mitigate youth sales.

“We are committed to preventing underage use of our product, and we want to be part of the solution in keeping e-cigarettes out of the hands of young people,” a Juul spokeswoman said in a statement. “Appropriate flavors play an important role in helping adult smokers switch. By working together, we believe we can help adult smokers while preventing access to minors, and we will continue to engage with the FDA to fulfill our mission.”

Juul did not respond to a question about whether the company tracks sales of its products by customer age.

The e-cigarette companies may have to take the fruit or candy-flavored products off the market, which would cut into sales significantly, according to an analyst note by Stifel, an investment firm that follows the tobacco industry. The four larger e-cigarette manufacturers, including Vuse, which is part of British American Tobacco, and Mark Ten XL, which is part of Altria, would be able to absorb the hit with minimal financial consequences because they also make traditional tobacco products. Juul, however, would have a harder time because it only makes vaping products.

Some studies indicate e-cigarettes may help adults addicted to cigarettes switch to a less harmful product with lower levels of toxins. But e-cigarettes also appear to be drawing in many teens who otherwise would not have started using nicotine if it were not for the flavors and other qualities of vaping, such as not burning the back of the throat or tasting or smelling unpleasant and sometimes affording use in places that ban smoking, like school bathrooms or classrooms.

“I’d hate for [Juul] to go out of business because I do think these products could potentially help adults if not quit then switch over to something that’s less risky,” said Dr. Mark Rubinstein, a UCSF pediatrics professor who researches nicotine dependence in adolescents and young adults. “I just don’t want to see kids using these products.”

“The trouble is how do we balance that?” he said. “How do we balance the harm reduction in adults with the harm creation for kids?”

Catherine Ho is a San Francisco Chronicle staff writer. Email: cho@sfchronicle.com Twitter: @Cat_Ho