Rapper Wiley has been dropped by his management following anti-Semitic posts on his social media accounts.
Wiley's Twitter account has been temporarily locked while Instagram said it had deleted some of his content, after a long series of posts on both platforms on Friday and Saturday.
The social media giants are facing growing pressure to close his accounts.
Police said they were looking at "relevant material" as critics accused Wiley of incitement to racial hatred.
Metropolitan Police officers in Tower Hamlets said in a statement: "We have received a number of reports relating to alleged anti-Semitic tweets posted on social media. The Met takes all reports of anti-Semitism extremely seriously. The relevant material is being assessed."
There are also calls for Wiley's MBE, appointed for services to music, to be forfeited.
Wiley, 41, known as the "godfather of grime", shared conspiracy theories and insulted Jewish people on his Instagram and Twitter accounts, which together have more than 940,000 followers.
In one tweet he said: "I don't care about Hitler, I care about black people", and also compared the Jewish community to the Ku Klux Klan.
On Instagram, videos of himself were interspersed with posts of screenshots - which have since been deleted - including one at about midday on Saturday suggesting Twitter has suspended him from tweeting for a week.
He had already been given a 12-hour ban on Friday night, but resumed tweeting on Saturday.
The platform has removed some of his tweets, with a note saying they violated its rules.
Wiley's manager, John Woolf, confirmed that the Twitter account, which is not verified, belongs to the London-born rapper, whose real name is Richard Cowie.
In a tweet on Friday evening that is no longer visible, Mr Woolf initially said he was "talking to him privately". He also said that, having known Wiley for 12 years, he knows "he does not truly feel this way".
But on Twitter on Saturday morning he tweeted: "Following Wiley's antisemitic tweets today we at @A_ListMGMT have cut all ties with him. There is no place in society for antisemitism."
The two men were pictured together in December with boxer Anthony Joshua.
In a subsequent statement, Mr Woolf said: "To be very clear here. I do not support or condone what Wiley has said today online in any way shape or form.
"I am a proud Jewish man and I am deeply shocked and saddened but what he has chosen to say.
"I am speaking to key figures in my community in light of today's tweets. This behaviour and hateful speech is not acceptable to me."
Wiley later claimed in a video posted on Instagram that he had "cut ties" with Mr Woolf - not the other way around.
Broadcaster and producer DJ Spoony criticised Wiley's "inflammatory" comments, tweeting that the artist "still has a huge role in our community but he must first see the error of his ways/comments and then make himself open to the help that will be offered".
The Ivors Academy, an association for music writers which gave Wiley its Inspiration Award in 2019, said "such appalling views have no place in the music creator community".
There has been growing outrage over the social media companies' responses.
The Campaign Against Antisemitism said it had reported Wiley to the Metropolitan Police and asked Twitter and Facebook, which owns Instagram, to close his accounts to "prevent further outpouring of anti-Jewish venom".
"We consider that Wiley has committed the offence of incitement to racial hatred, which can carry a substantial prison sentence," a statement read.
It added that it would contact the Cabinet Office to ask for his MBE be forfeited.
Lord Mann, an adviser to the government on anti-Semitism, called on Twitter and Instagram to remove him from their platforms.
He said some of the content glorifies a violent attack on a rabbi in London, adding: "That breaches all their standards, it's not even marginal."
Luciana Berger, a Liberal Democrat politician who left the Labour Party over anti-Semitism last year, said the "bile... permeates impressionable (often younger) minds".
Actors David Baddiel and Tracy-Ann Oberman, who are both Jewish, also called for more action.
Facebook, which owns Instagram, said in a statement: "There is no place for hate speech on Instagram. We have deleted content that violates our policies from this account and are continuing to investigate."
Twitter said Wiley's account had been temporarily locked "for violating our Hateful Conduct policy".
"Abuse and harassment have no place on our service and we have policies in place - that apply to everyone, everywhere - that address abuse and harassment, violent threats, and hateful conduct," it added.
"If we identify accounts that violate any of these rules, we'll take enforcement action."
Wiley first entered the UK singles charts with Wearing My Rolex in 2008. His subsequent hits include Heatwave in 2012 and Boasty in 2019, a collaboration with rappers Stefflon Don and Sean Paul and actor Idris Elba.