The report comes a day after Musk endorsed an antisemitic post on X that falsely claimed members of the Jewish community were stoking hatred against white people.
Media watchdog Media Matters said it found that corporate advertisements by IBM, Apple (AAPL.O), Oracle (ORCL.N) and Comcast's (CMCSA.O) Xfinity were being placed alongside antisemitic content.
"IBM has zero tolerance for hate speech and discrimination and we have immediately suspended all advertising on X while we investigate this entirely unacceptable situation," IBM said in a statement.
Apple, Oracle and Xfinity did not immediately respond to requests for comment.
X said its system does not intentionally place brands "actively next to this kind of content", and the content cited by Media Matters would no longer be able to make money off its posts.
Musk's Wednesday comments on the social media platform are not the first time he has engaged in discussions that reference antisemitic tropes or conspiracy theories. X declined to comment and referred to a statement from CEO Linda Yaccarino posted Thursday.
"When it comes to this platform - X has also been extremely clear about our efforts to combat antisemitism and discrimination. There's no place for it anywhere in the world - it's ugly and wrong. Full stop," said Yaccarino.
On Wednesday, after being questioned by another user about targeting all Jewish people, Musk attacked the Anti-Defamation League, a nonprofit that works to fight antisemitism, who he has accused previously without evidence of being responsible for the drop in advertising on X.
ADL CEO Jonathan Greenblatt responded on X that “at a time when antisemitism is exploding in America and surging around the world, it is indisputably dangerous to use one's influence to validate and promote antisemitic theories.”
Advertisers have fled the site since Musk bought it and reduced content moderation that has resulted in a dramatic increase in hate speech on X, civil rights groups have said.
Musk is also CEO of electric carmaker Tesla (TSLA.O), which has been hit by several lawsuits that allege rampant racial or sexual harassment of workers.
Antisemitism has been on the rise in recent years in the United States and worldwide. Following the outbreak of war between Israel and Palestinian Islamist group Hamas, which attacked Israel on Oct. 7, antisemitic incidents in the United States rose by nearly 400% from the year-earlier period, the ADL said.
(This story has been corrected to fix typo in paragraph 1)
