Facebook CEO Mark Zuckerberg has rebuked his own staff for crossing out "Black Lives Matter" slogans on the walls of the company HQ in Menlo Park, San Francisco.
On several occasions, employees had replaced the slogan with "all lives matter" on a large signature wall in which staff are encouraged to write comments, according to an NBC News report, prompting Zuckerberg to issue a company-wide memo.
NBC News has confirmed the validity of the internal posting sent to Facebook employees.
"'Black lives matter' doesn't mean other lives don't – it's simply asking that the black community also achieves the justice they deserve," Zuckerberg wrote.
Zuckerberg pointed out to his workers that it wasn't the first time that he had highlighted the problem.
"Despite my clear communication at Q&A last week that this was unacceptable, and messages from several other leaders from across the country, this has happened again," Zuckerberg said in the memo.
Further comments revealed the CEO's anger.
"I was already very disappointed by this disrespectful behavior before, but after my communication I now consider this malicious as well," he said.
The phrase "Black Lives Matter" was first written by activist Alicia Garza in a Facebook post.
It followed the 2013 acquittal of George Zimmerman, the Florida man who shot and killed African American teenager Trayvon Martin.
In its latest diversity report, Facebook reports less than 1.5 percent of its staff are black or African-American.
The report also highlights that across the U.S. technology industry, black employees make up just one percent of the workforce.
Zuckerberg has encouraged employees to participate in a company meeting scheduled for Friday March 4.
In the post he says the meeting will help staff "to educate themselves about what the Black Lives Matter movement is about".
CNBC contacted Facebook for comment on the issues who responded by saying it had nothing further to add at this stage.