The Chinese-owned video sharing app TikTok – and its "completely open" messaging system – is being investigated by the UK's information commissioner.
Owned by Beijing-based ByteDance, TikTok allows users to upload 15-second video clips of themselves which can be enhanced by using filters or other special effects.
There are concerns that young children may be using the app and seeing harmful content.
Information Commissioner Elizabeth Denham told MPs on the digital, culture, media and sport committee that she was looking at the "transparency tools for children" and the "kind of videos that are collected and shared by children online".
As of March this year, TikTok had been downloaded more than a billion times, with more than 500 million active users.
In February, America's Federal Trade Commission (FTC) fined TikTok $5.7m (£4.5m) for allegedly collecting information from kids under 13 who are not supposed to use TikTok.
"The operators of Musical.ly – now known as TikTok – knew many children were using the app but they still failed to seek parental consent before collecting names, email addresses, and other personal information from users under the age of 13," FTC chairman Joe Simons had said.
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It was the "largest civil penalty ever obtained by the commission in a children's privacy case", the FTC claimed.
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