President Donald Trump continued challenging big tech companies on Tuesday, warning them about censoring content from conservatives.

“I think what Google and what others are doing – if you look at what is going on with Twitter and if you look at what’s going on in Facebook, they better be careful because you can’t do that to people,” Trump said. “You can’t do it.”

The president said that he had heard “thousands” of censorship complaints from people and repeated that it was “not fair.” He added that censorship was a “serious charge” against the tech companies.

“I think that Google and Twitter and Facebook, they are really treading on very, very troubled territory and they have to be careful,” he said. “It is not fair to large portions of the population.”

The president has recently ramped up his criticisms of the social media companies after reports of conservative content being downgraded, removed, or deleted from their platforms.

Axios reporter Jonathan Swan suggested on Twitter that the president was reacting to a series of Breitbart News stories on the biased search results and censorship by tech companies.

It *appears* these articles — which have been spinning around conservative circles — are the ones that got Trump spun up: https://t.co/Kcg0kKveTH // https://t.co/tcVNHSPvCL — Jonathan Swan (@jonathanvswan) August 28, 2018

On Tuesday morning, the president commented on a report that argued Google was favoring liberal and establishment media sources on their Google News searches and burying conservative content.

Google search results for “Trump News” shows only the viewing/reporting of Fake News Media. In other words, they have it RIGGED, for me & others, so that almost all stories & news is BAD. Fake CNN is prominent. Republican/Conservative & Fair Media is shut out. Illegal? 96% of…. — Donald J. Trump (@realDonaldTrump) August 28, 2018

….results on “Trump News” are from National Left-Wing Media, very dangerous. Google & others are suppressing voices of Conservatives and hiding information and news that is good. They are controlling what we can & cannot see. This is a very serious situation-will be addressed! — Donald J. Trump (@realDonaldTrump) August 28, 2018