It took grown-ups a while to catch on to the teen video craze TikTok. As always, they are now threatening to ruin the fun.

Blame China. US lawmakers do. The Chinese startup ByteDance Technology did not seek approval from the Committee on Foreign Investment in the United States when it bought the social media company Music.ly for $1bn in 2017 and turned it into the looping video app TikTok. Now Cfius is investigating the deal.

TikTok’s addictive short videos are popular all over the world. It has been downloaded more than 110m times in the US alone. But the company’s set-up is awkward. The Beijing based mega-startup ByteDance runs two versions of the same app. In China it is called Douyin. Elsewhere it is TikTok. Content is largely kept apart. Revenues are dominated by the Chinese version. But that could change as TikTok tries to ramp up its advertising business.