Google fired a top AI researcher on Friday, the second high-level departure to shine an unwelcome spotlight on both its management of sensitive artificial intelligence issues and wider internal discontent over race and diversity.

The internet group said Margaret Mitchell, who had been co-head of its AI ethics group, had been dismissed over “multiple violations of our code of conduct” and security policies. These included the “exfiltration of confidential business-sensitive documents and private data of other employees”, it said.

The move comes two months after the departure of Timnit Gebru, the other head of the ethics group, which was formed to lead research into new techniques for making sure the company’s AI technology was used in a fair and unbiased way.