Stephen Colbert is to be investigated by the Federal Communications Commission (FCC) over a joke about President Donald Trump.
The FCC chairman Ajit Pai said the commission received several complaints about the monologue, which some viewers branded homophobic.
It concerned references involving Donald Trump and Vladimir Putin.
On Twitter, angry users set hashtag #FireColbert trending worldwide.
Ajit Pai told radio host Rich Zeoli he had now had a chance to watch the controversial clip, which aired on Stephen Colbert’s The Late Show on May 1.
“We have received a number of complaints,” he said.
“We’ll follow the standard operating procedures, as we always do, and make sure we evaluate what the facts are and apply the law fairly and fully.”
CBS could be fined if the FCC decides that Stephen Colbert’s joke was indecent.
The FCC definition includes remarks that appeal to “an average person’s prurient interest and, taken as a whole, lack serious literary, artistic, political or scientific value”.
Despite demands for him to be fired over the alleged slur, Stephen Colbert said on May 3 that he would change “some of the words” in the monologue but did not regret it.
Stephen Colbert then offered an olive branch to the LGBT community, saying: “Anyone who expresses their love for another person in their own way is, to me, an American hero.”
One Trump supporter who took part in the movement #GaysForTrump, tweeted on May 3 that Stephen Colbert’s original rant was “homophobic” and “disgusting”, while others repeated calls for his sacking.
However, many defended the comedian.
Others noted that Donald Trump had himself been recorded using inappropriate language.
Former Republican Governor and presidential hopeful Mike Huckabee argued that Stephen Colbert should be protected by the First Amendment, which enshrines the right to free speech in the US.