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 are speculating 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 on Sunday she had deleted her TikTok account because the app was under new ownership and we are being completely censored and monitored.
Similar views have been echoed across social media, with many US users questioning in posts whether the app is cooked.
RIP TikTok 2016-2026, one user wrote in a post on Reddit.
Users of the video-sharing app in the US have been posting on social media about problems throughout the outage, which began on Sunday.
Platform outage monitor Downdetector told the BBC it had received 663,061 reports of issues from US users of TikTok 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.
As part of President Donald Trump's deal allowing TikTok to continue operating in the US, Oracle will inspect and retrain a separate version of its algorithm for American users.
