The US government has launched a criminal investigation into TikTok's parent company, ByteDance, over improper access to the personal information of several US citizens, according to Forbes and The New York Times.

News of the investigation, which reportedly involved a subpoena to ByteDance along with a number of interviews by the FBI, comes after TikTok confirmed in December that four ByteDance employees had been fired in connection with the incident, following an internal review.