More than 1,400 Google employees on Friday demanded that the tech giant explain why it dismissed a Black artificial intelligence ethics researcher.

Timnit Gebru tweeted early in the week that Google told her a resignation she had not proffered was accepted, after she sent a message to an internal group lamenting the “silencing of marginalized voices.”

She had also told the “Brain Women and Allies” group in the email that she had been ordered to retract a research paper.

Gebru is an outspoken diversity advocate and co-founder of a group devoted to increasing Black talent in artificial intelligence.

Until Tuesday, she was a staff researcher and co-lead of an ethical AI team at Google.

Gebru tweeted what she said was the dismissal message from Google, which noted that “aspects of the email you sent last night to non-management employees in the brain group reflect behaviour that is inconsistent with the expectations of a Google manager.”

The research paper Gebru was told to retract looked at the potential for an AI tool used by Google and other tech firms to imitate human writing of hate speech and biased language, according to an NPR report.

Slightly more than 1,400 Google employees were among the nearly 3,300 names on an online letter calling on the tech giant to explain Gebru’s dismissal along with the reason for ordering her to withdraw her research.

The letter demanded Google make an “unequivocal” commitment to research integrity and academic freedom.

“Instead of being embraced by Google as an exceptionally talented and prolific contributor, Dr Gebru has faced defensiveness, racism, gaslighting, research censorship, and now a retaliatory firing,” the letter contended.

In response to a request for comment, Google referred AFP to an email by AI division leader Jeff Dean to researchers at the company that he posted publicly on Friday.

Dean said in the email it was a “difficult moment” and he wanted to clear up what he saw as “a lot of speculation and misunderstanding on social media” about Gebru’s departure from the company.

The research paper authored by Gebru and other researchers was shared for review just a day before a submission deadline and “had some important gaps that prevented us from being comfortable putting Google affiliation on it,” Dean said in the email, a copy of which was posted online.

Gebru responded with conditions — including that Google give her the names of everyone involved in reviewing the paper — saying she would leave if they were not met, Dean contended.

“We accept and respect her decision to resign from Google,” Dean said in the email.

“Given Timnit’s role as a respected researcher and a manager in our Ethical AI team, I feel badly that Timnit has gotten to a place where she feels this way about the work we’re doing.”

Gebru, who is Ethiopian American, earned engineering degrees and a doctorate from Stanford University in Silicon Valley. She has worked at Apple and conducted research at Microsoft.

Gebru’s research has included showing the likelihood of facial detection technology making mistakes when identifying people of color.

Her dismissal came just days after a US labour board complaint accused Google of using surveillance, interrogation and other tactics to spy on activist employees.

The National Labor Relations Board (NLRB) complaint stemmed from the dismissal a year ago of a quartet of employees dubbed the “Thanksgiving Four.”

The workers sought a federal investigation into their dismissal, alleging they were sacked in retaliation for their labour organizing efforts, while Google maintained the employees had violated data security policies.