NEW HAVEN — To counter a “crisis of youth vaping” across the country, Attorney General William Tong said Connecticut is among leaders of an investigation by 39 states into Juul Labs with a focus potentially on unfair and deceptive marketing practices.

It is an expansion of an investigation by Connecticut in 2019 that focused on marketing practices and Juul’s claims that it is “a smoking cessation tool,” as well as programs that targeted veterans, as well as employers and workplaces.

Tong said they are “digging in” on what Juul is saying about its product, especially that it is a smoking cessation tool that helps people stop smoking.

“Now they say they are not a smoking cessation tool, they are a switching tool. I think that is interesting language,” the attorney general said.

“If you use your common sense and watch their videos and look at their social media posts and what they are doing marketing across media and across platforms, that clearly what they are trying to tell you is that it is an alternative product that can help you stop smoking,” Tong said.

Tong, made the national announcement from James Hillhouse High School, where a group of students offered some advice on how to reach young people

Tong said there has been a 20 percent to 30 percent spike in vaping in Connecticut in a short time.

The 2019 National Youth Tobacco Survey results showed “more than 5 million youth reporting having used e-cigarettes in the past 30 days” and nearly 1 million reporting daily use, according to fda.gov.

The attorney general was asked whether he had seen internal emails or documents that led him to believe the companies were targeting kids. “Yes we are collecting documents. I’m not ready yet to disclose what we found in specific terms, but what we have seen has us very concerned,” he said.

He said they want to know what role the companies have played in the epidemic, especially Juul, given that it dominates 80 to 90 percent of the market.

“They pretty much are the whole ballgame,” Tong said.

In Connecticut’s 2019 probe, it uncovered “a lot more information and evidence” which compelled him to expand the probe with other states. “We are stronger together always,” Tong said.

Juul released a statement saying it has halted television, print and digital advertising and eliminated most flavors in response to concerns by government officials and others.

“We will continue to reset the vapor category in the U.S. and seek to earn the trust of society by working cooperatively with attorneys general, regulators, public health officials, and other stakeholders to combat underage use and transition adult smokers from combustible cigarettes,” the statement said.

Michelle Seagull, who heads the state Department of Consumer Protection, said “truth in advertising, truth in marketing” is necessary across the board, but particularly products that are used by young people.

Tong said what they found is that vaping is being taken up by middle school children, in addition to high school teens.

“It is a very serious problem across the country,” the attorney general said. He said as the investigation continues he expects more civil investigative demands or subpoenas will be issued.

He said the best thing that Juul can do is “respond fully, forthrightly and cooperate with us.”

Tong said the damage has already been done and he wants to know to what extent Juul and others are responsible for the “youth vaping epidemic that is sweeping the country ... we are going to hold them accountable.”

He said they are moving quickly, but thoroughly.

Tong said there are similarities with Big Tobacco, but the scale of Big Tobacco was “so much bigger” than the vaping and pharmaceutical markets.

But in terms of “marketing practices, potentially targeting young people, the way people get addicted and the product itself — a nicotine product — all those similarities are real,” Tong said.

He said if there were litigation and a settlement, that money would go to prevention, education and treatment.

New Haven Mayor Justin Elicker said the cultural change over decades where smoking was once ubiquitous is due to education and because Big Tobacco was held accountable.

Elicker told the roundtable of Hillhouse juniors and seniors that this was an opportunity for them to look into the future and a role they could play “pushing back on some of these, in my opinion, inequities that exist out there.”

He told them through politics and government, everyone can advocate for justice and their discussion was part of that.

Kuniya Asobayire, 17, a senior, told Elicker and Tong the dangers of vaping should be put into the curriculum. “Education through the school’s curriculum makes students really know, not just having resources down the street because no one is going to go to them.”

Amia Lott, another senior, said she feels students vape or use marijuana to reduce anxiety.

Ralphael Hawkins, who runs track, said he has seen top athletes in his school basically lose their skills when they take up vaping. Another student said student-led discussions on the topic would be effective.

The Associated Press contributed to this story.