US President Donald Trump has warned Google, Twitter and Facebook they are "treading on troubled territory" amid a row over perceived bias.
He said they had to be "very careful", after earlier accusing Google of rigging the search results for the phrase "Trump news".
An aide said the administration was "looking into" the issue of regulation.
Google said its search engine set no political agenda and was not biased towards any political ideology.
Speaking to reporters at the White House, Mr Trump said Google had "really taken a lot of advantage of a lot of people, it's a very serious thing".
Adding the names of Facebook and Twitter, he said: "They better be careful, because you can't do that to people... we have literally thousands of complaints coming in."
He gave no details of what action he might take.
However, when asked earlier about Google, Mr Trump's top economic adviser, Larry Kudlow, said the administration was "taking a look" at whether it should be regulated and would do "some investigation and some analysis".