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Uber’s self-driving arm — now called the Advanced Technology Group — has seen a number of structural changes in the past few months, including the departures of some of its top engineering talent.

Among the recent exits is the head of its mapping team, Brett Browning, and the head of its autonomy and perception team, Drew Bagnell, three sources have told Recode. The departures were announced in an email Uber sent its employees the first week of December.

In September, Peter Rander, an engineering lead who specializes in the commercialization of robotics, also left the company. The three engineers were poached by Uber from Carnegie Mellon, Carnegie Robotics or the National Robotics Engineering Center, which is affiliated with Carnegie Mellon University, in January 2015.

It’s not clear what the next step is for the engineers, though Rander lists himself on LinkedIn as a robotics and self-driving technology consultant.

The moves come following Uber’s acquisition of self-driving trucking company Otto in August, which put co-founder Anthony Levandowski in charge of the company’s autonomous efforts above existing directors Raffi Krikorian — who was previously at Twitter and joined Uber in March 2015 — and John Bares — who was poached from Carnegie Robotics in January 2015.

It also comes at a time when Uber is doubling down on its self-driving efforts with both the soft launch of its UberFreight service and the self-driving pilot in Pittsburgh, as well as the acquisition of artificial intelligence and machine learning research startup Geometric Intelligence.

As part of the acquisition, Uber established an AI lab to be headed up by the founding CEO of Geometric Intelligence, Gary Marcus. Artificial intelligence and machine learning are crucial aspects of any self-driving system, but the company expects the AI lab to serve across various departments as it begins to automate more of its services — including its logistics and routing platform.

Just a day after Uber announced the acquisition, however, the head of its machine learning team, Danny Lange, announced he had left and joined video game startup Unity Technologies. In September, Uber also saw the departure of its head of applied machine learning, Marcos Campos. Campos left to be the head of AI at a startup called Bonsai that pitches itself as a platform that makes it easy to integrate machine learning into apps.

Johana Bhuiyan is the senior transportation editor at Recode and can be reached at johana@recode.net or on Confide, WeChat, or Telegram at 516-233-8877.

It’s a difficult time to lose key self-driving and machine learning talent for any company, as more players enter the race to develop autonomous cars. Established companies like Google, Apple, Ford and GM are increasingly competing with newcomers like Zoox, Faraday Future and now Chris Urmson’s new self-driving company for engineers with skills in a field that is relatively new.

Uber declined to comment for the story.