The Democratic governor of California, Gavin Newsom, has announced an investigation into claims TikTok has censored content which is critical of the Trump administration.
A deal was concluded last Thursday to split off the US operation of the app - three days later thousands of American users began reporting problems including seeing 'zero views' on new posts.
Many also reported being unable to see political posts, such as content criticising the shooting by federal agents of Alex Pretti in Minneapolis on Saturday.
TikTok has not commented on accusations this is related to last week's deal, blaming user problems on a 'major infrastructure issue' relating to a data centre power outage.
However, Newsom's office says it has received confirmed reports of TikTok suppressing content critical of President Trump.
Following TikTok's sale to a Trump-aligned business group, our office has received reports - and independently confirmed instances - of suppressed content critical of President Trump, wrote the California governor's office on X on Monday.
It said Newsom would be 'launching a review of this content' and probe whether the company had violated the state's laws.
The BBC has asked TikTok's new US parent company, TikTok USDS Joint Venture LLC, for a response.
Newsom declared earlier on Monday it was 'time to investigate' TikTok over censorship concerns.
His post linked to another X user's post containing a screenshot from TikTok, that appeared to show the video-sharing app flagging up a message they tried to send saying 'Epstein'.
The same flag seemingly appeared for other US TikTok users when they tried to message others with the surname of convicted sex offender Jeffrey Epstein, according to social media posts seen by BBC News.
Many users speculate that this, combined with some political content not displaying in the app's For You feed or in search, may be censorship by TikTok's new US owners - with investors and directors some believe have ties to Trump.
Celebrities have also spoken out over similar concerns about the app. Hacks actress Meg Stalter told Instagram followers she had deleted her TikTok account because the app was 'under new ownership and we are being completely censored and monitored.'
'RIP TikTok 2016-2026,' one user wrote in a post on Reddit. 'Seems like TikTok might be dead after the US purchase.'
Meanwhile, users of the video-sharing app in the US have been posting about problems throughout the outage, which began on Sunday. Platform outage monitor Downdetector reported over 660,000 issues from US TikTok users between Saturday and Monday.
TikTok's US owner said on Monday users may notice 'multiple bugs, slower load times or timed-out requests' as it worked to resolve issues triggered by a power outage at one of its data centre partner Oracle's sites.
'While the network has been recovered, the outage caused a cascading systems failure that we've been working to resolve together with our data centre partner,' it said.
