Such apps can capture a child's physical location, phone numbers of their friends and more.
The FTC described the marketplace for mobile applications - dominated by online stores operated by Apple and Google - as a digital danger zone with inadequate oversight. In a report by the FTC's own experts, it said the industry has grown rapidly but failed to ensure that the privacy of young consumers is adequately protected.
The FTC did not say which or how many companies it was investigating.
