These days it's hard to find an American teenager who isn't glued to their smartphone, and while parents can't be sure what their kids are getting up to every minute of the day, it's important to know your child is being safe on line.

That's why so many parents, community groups, police departments, and even the FBI are warning about the risks of a new app called Yellow. Marketed to teens aged 13-19, Yellow is an app that lets kids connect with more than 7 million users worldwide.

Parents worry that the app's design - swipe right to connect or swipe left to not connect - is borrowed from the adult dating app Tinder. They're concerned that this "Tinder for teens" will become a hot spot for child predators.

Some parents have even made their own accounts on the app, to test its safety features and see what teens were posting.

What they found shocked them.

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One parent who tested the app said she saw "girls that wore provocative tops. There were some boys that didn't have shirts on. And if I'm a predator, whether it's male or female, this is a prime area to find a potential target, and make that contact."

A group of reporters put the app's security features to the test when they made a fake account for a 17-year-old girl named Samantha. The app didn't check her real age in any way, or make sure she had her parent's permission to log on.

Other parents revealed their children have been sent lewd and hurtful messages while using the app. A mother shared this message sent to her teenage daughter: "ugly or not, will still take you."

Despite warnings from police that the app puts children at risk, Yellow says they're "moving fast to ensure it is on par with industry standards for safety and security."

The company has hired an online safety expert and insists their product is only meant "to help teens 13 years and over to make friends with other teens," but that's not enough for some parents.

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