A group of senators is urging the Food and Drug Administration to take actions to stop leading e-cigarette Juul from becoming even more popular among kids and teens.

Media reports have detailed how adolescents around the country are using Juul and bringing the sleek devices that look like USB drives to school. Advocates have expressed their concerns about how fruity flavors may mask the reality that one pod of liquid contains as much nicotine as that in a pack of cigarettes.

Eleven Democratic senators — including Senate Minority Leader Chuck Schumer, Senate Democratic Whip Dick Durbin, Elizabeth Warren and Tim Kaine — are urging FDA Commissioner Scott Gottlieb to ban sweet nicotine flavors they say could entice young people. Last month, the FDA took the first step toward implementing a rule about the role that flavors play in attracting users to certain tobacco products.

"It is imperative that the FDA take immediate steps to remove kid-friendly e-cigarette and cigar flavorings from the market. If companies want to use flavors, they should be required to demonstrate to the FDA that use of flavors will benefit public health," the senators wrote in their letter.

The senators are also pressing the FDA to reverse its decision to delay regulation of e-cigarettes and some tobacco products. Last summer, the agency extended the deadline as part of a sweeping plan to overhaul tobacco regulation. Under the revised timeline, manufacturers won't need to file until 2021 for combustible products like cigars and until 2022, for noncombustible products like e-cigarettes.

Last month, anti-tobacco groups and public health organizations sued the FDA for the delay.

Six organizations, including Campaign for Tobacco-Free Kids and Truth Initiative, sent a separate letter to the FDA on Thursday asking the agency to take a number of actions, including ordering the removal of some flavors and suspending online sales until the company establishes "adequate rules" to verify customers are of legal age.

"I mean, this is more than an isolated incident," Truth Initiative CEO Robin Koval told CNBC. "It has become a nationwide phenomenon. I don't know how else to say it. It's very, very disturbing."

In a congressional hearing Tuesday, Gottlieb said the agency is "deeply concerned" about youth use of e-cigarettes. He said the FDA is going to take some "very vigorous enforcement steps" in the coming weeks.

"You'll see the agency stepping into this fight very soon," he said.

The senators wrote a separate letter to Juul Labs, the company that manufacturers Juul, asking CEO Kevin Burns how the product is marketed to kids and teens, what ingredients are in the flavored pods, as well as requesting the company take steps to limit youth use.

In a statement, Burns said he received the letter and takes this matter "very seriously." The company has been finalizing a plan for new initiatives and actions, which it will announce it in coming weeks.

"I share the concerns expressed in this letter about youth access and believe no young person should ever try JUUL," Burns said in an emailed statement. "I look forward to discussing and working with members of Congress, the FDA and others about how we can make progress on preventing youth from ever using JUUL or other nicotine products."

Like other e-cigarette makers, Juul says its products are meant for adult smokers who are looking to switch from conventional products. In response to reports of adolescents using its products, the company has invested in education and prevention efforts such as "secret shoppers" who test to make sure retailers are not selling to minors.

"It's a really, really important issue," Juul Labs' chief administrative officer Ashley Gould told CNBC in December. "We don't want kids using our products."