The US Justice Department said on Wednesday it would probe social media giants over concerns over competition and “stifling the free exchange of ideas.”

The announcement comes days after President Donald Trump accused big technology firms of censoring and suppressing conservative voices, allegations strongly denied by the companies.

A Justice Department statement said Attorney General Jeff Sessions “has convened a meeting with a number of state attorneys general this month to discuss a growing concern that these companies may be hurting competition and intentionally stifling the free exchange of ideas on their platforms.”

The brief statement, which came at the conclusion of a Senate hearing including top executives of Facebook and Twitter, offered no clues on whether officials were considering an antitrust investigation or some form of regulatory action.

Tech industry analysts say there is little evidence internet firms are filtering content for political reasons, but that the companies would have constitutional protections against any government effort to regulate their algorithms.

On Tuesday, Federal Communications chairman Ajit Pai said Silicon Valley firms to provide more transparency about how they operate, raising the possibility of tougher regulations for technology firms.

“We need to seriously think about whether the time has come for these companies to abide by new transparency obligations,” Pai said in a blog post.

Pai offered no specific proposals, but appeared to echo concerns raised by Trump, who claimed tech firms may be biased against conservatives.

“Consumers interact with these digital platforms on a daily basis. We get our news from them. We interact with our family and friends on them,” Pai wrote.

Trump last week issued a warning to Google, Facebook and Twitter to “be careful” but stopped short of calling for regulation.

Twitter chief Jack Dorsey rejected any suggestion of political bias in comments prepared for a House of Representatives hearing Wednesday.

“Twitter does not use political ideology to make any decisions, whether related to ranking content on our service or how we enforce our rules,” Dorsey said in his written testimony.

“We believe strongly in being impartial, and we strive to enforce our rules impartially.”

Google and Facebook have made similar points.

Daniel Castro of the Information Technology and Innovation Foundation said the intent of the statement was not clear but that the statement was worrisome.

“Social media platforms have the right to determine what types of legal speech they will permit on their platforms,” Castro told AFP.

“The federal government should not use the threat of law enforcement to limit companies from exercising this right. In particular, law enforcement should not threaten social media companies with unfounded investigations for booting white nationalists like Richard Spencer off their platforms.”