Where there’s smoke, there’s fire.

That seems to be a growing concern when it comes to e-cigarettes.

Earlier this week, a 14-year-old girl was injured at a Florida amusement park when an electronic cigarette being used by another person exploded while they were on a ride together.

Officials at the Food and Drug Administration (FDA) say that explosion wasn’t an isolated incident.

The federal officials said they are aware that between 2009 and January 2016 there were at least 134 reported incidents of e-cigarettes overheating, catching fire, or exploding.

Of those, 56 happened in 2015 and 10 were reported in January.

FDA officials told Healthline they believe these figures are “an underestimate of actual events.”

In August, the FDA began regulating e-cigarettes and other vaping products.

With that authority, FDA officials have started to gather information in an attempt to come up with regulations to govern the safety of e-cigarettes.

“The FDA remains concerned about adverse events associated with the use of electronic nicotine delivery systems (ENDS), such as e-cigarettes, including overheating and exploding batteries as reported in the news,” Michael Felberbaum, an FDA press officer, told Healthline in an email.

Read more: E-cigarette industry survival depends on legal loopholes »

Batteries are the focus

Most of the e-cigarette explosions have been linked to the lithium batteries used inside the vaping devices.

The situation is similar to what authorities believe caused fires on hoverboards as well as explosions and fires involving mobile phones.

The problem is the lithium batteries in e-cigarettes sit close to the combustible liquids used in those products.

In addition, e-cigarettes are held close to a person’s face.

Felberbaum said the pending FDA regulations could include wattage, battery type, testing, and voltage lockout protections.

Officials at the Smoke-Free Alternatives Trade Association (SFATA), which represents the vapor product industry, said they take the reports of e-cigarette explosions seriously but note that “millions of former smokers across the United States and overseas continue to use vapor products as intended.”

In an email statement to Healthline, the association stated, “We cannot speak to user error or on behalf of a manufacturer for their device. If there is truly an issue with a specific device, similar to a laptop or cell phone manufacturer, inquiries should be directed toward the individual company.”

Among other things, SFATA recommends e-cigarette users refrain from using incompatible batteries and chargers, keep the device away from extreme temperatures, and not let the device or batteries come in contact with metal objects such as coins, keys, or jewelry.

Read more: E-cigarette use among teens continues to rise »

Lawsuits abound

E-cigarette explosions and fires have resulted in a number of legal actions.

In March, a California woman filed a lawsuit against the retailer who sold her e-cigarettes after one of the devices exploded after she put in new batteries.

The woman told The Wall Street Journal that the explosion ripped a hole in her mouth and spewed battery acid across her body.

The Journal reported that lawsuit is one of dozens filed in California, Florida, New York, and other states. In many of these cases, the legal action is directed against retailers and other U.S.-based companies because most of the battery manufacturers are in China.

In October 2015, a jury in Southern California awarded a woman $1.9 million in her lawsuit against an e-cigarette retailer, distributor, and wholesaler. The woman said she was severely burned when an e-cigarette device caught fire while it was being recharged inside her car.

In March, the U.S. Department of Transportation issued new rules that prohibit passengers and crew members from storing battery-powered portable electronic smoking devices in checked baggage. It also bans them from charging the devices or batteries onboard an aircraft.

Read more: E-cigarette flavorings carry lung-corroding materials »

What about health risks?

The actual health risks associated with using e-cigarettes continue to be debated.

The latest research doesn’t shed a lot of light on the situation.

A study, published this week in the New England Journal of Medicine, states it’s not possible at the moment to reach a consensus on the safety of e-cigarettes or whether they are an effective tool for people trying to stop smoking.

The researchers note that part of the problem is the 466 different brands and 7,764 unique flavorings of e-cigarettes.

One expert who looked at the study said the work is an “excellent review” given the limited data.

“There are risks associated with smoking e-cigarettes, but likely less than with smoking tobacco cigarettes,” Dr. Christine Cho, an assistant professor of medicine at National Jewish Health for Kids, said in an email to Healthline. “The effectiveness of e-cigarette use as a method to quit smoking tobacco cigarettes is not known.”

This week’s study follows a report in April by the Royal College of Physicians in England that concluded vaping e-cigarettes is far healthier than smoking regular cigarettes.

However, a lawsuit filed in November 2015 by an environmental watchdog group stated that several brands of e-cigarettes, e-liquids, and other vaping products give off high levels of two cancer-causing chemicals.

And, two studies published in April 2015 concluded that e-cigarette use actually hurts efforts to quit smoking.

The stakes are high in both determining whether e-cigarettes are a health hazard or a safety hazard.

The e-cigarette industry is estimated to now be $3.5 billion … and growing.