The Democratic governor is one of Trump's most vocal critics and has accused the president's administration of curbing basic freedoms in the United States.

"It's time to investigate. I am launching a review into whether TikTok is violating state law by censoring Trump-critical content," Newsom posted on X.

TikTok announced last week it had established a new joint venture to operate its US business, which would reduce its Chinese ownership to 19.9 percent and put majority control in the hands of mainly American businesses including Trump allies.

The company said the issues raised were due to a "cascading systems failure" linked to a data center power outage and that reports of any other cause would be "inaccurate."

Washington has long sought to tighten control over TikTok, citing national security concerns over the platform's Beijing-based parent company, ByteDance.

"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," Newsom's office wrote on X.

Newsom shared a screenshot appearing to show a TikTok user unable to send a message reading "epstein" because it violated the platform's community guidelines.

Trump's past friendship with sex offender Jeffrey Epstein has brought intense scrutiny to the president.

Allegations of so-called shadowbanning by the app also cropped up in the hours after Border Patrol agents on Saturday shot and killed Alex Pretti, a 37-year-old intensive-care nurse.

Singer Billie Eilish said "tiktok is silencing people btw" on her Instagram account, screenshotting her brother Finneas O'Connell's TikTok video about Pretti's death that logged fewer viewers than usual.