Google struggled on Thursday to limit the fallout from the departure of a top artificial intelligence researcher after the Internet group blocked the publication of a paper on an important AI ethics issue.

Timnit Gebru, who had been co-head of AI ethics at Google, said on Twitter that she had been fired after the paper was rejected.

Jeff Dean, Google’s head of AI, defended the decision in an internal email to staff on Thursday, saying the paper “didn’t meet our bar for publication.” He also described Dr. Gebru’s departure as a resignation in response to Google’s refusal to concede to unspecified conditions she had set to stay at the company.