An alarming number of kidnappings, rapes and murders have been linked to messaging applications that can easily be downloaded onto smartphones for free by pre-teens and teens. Police are warning about one especially popular mobile chat app called Kik, which the creator claims is used by 40% of US teens.

Chats on Kik pose a greater danger, experts warn, because it is easier for a predator to remain anonymous. Just an email is needed to sign up, which means no phone number is connected to the account.

The latest criminal case involves a missing Michigan teen who is believed to have boarded a Greyhound bus last week with a man she supposedly met in a Kik app chat. Sixteen-year-old Joy Dene Martin of Saugatuck, Michigan, may be traveling out of state, according to Michigan State Police.

Also read our story, URGENT! Endangered teen left with stranger she met on anonymous messaging app

Nancy Grace and Alan Duke explore the dangers in this episode of “Crime Stories with Nancy Grace.”