A teenage Bronx girl has been missing for more than a week, her mother says, and may have been secretly chatting on a smartphone app before leaving.

Jessica Santiago says her 13-year-old daughter, Aaliyah Thomas, got up late at night last Thursday and left home.

The teen, who is diabetic, took a bag containing a supply of insulin expected to last several days. But she left her cellphone behind, on which Santiago says she found her daughter had traded risque photos with strangers through an app called MeowChat.

"I talked to her constantly about the dangers of speaking to people online," Santiago says. "Right now I am at a loss for words, because I never expected my 13-year-old daughter to do such a thing."

The teen left home wearing a black and gray hooded sweatshirt, black skirt and black shoes. She has dark hair and brown eyes, stands around 5 feet 6 inches tall and weighs 185 pounds.