Apple’s effort to build its own self-driving car has hit some more speed bumps in recent weeks.

Some of the best minds working on Apple’s Project Titan team have reportedly left the iPhone-maker to join one of the hottest autonomous vehicle start-ups in Silicon Valley.

Based on a new report from Bloomberg, it appears that a group of 17 engineers has been hired away from Apple by the self-driving car start-up Zoox Inc. The exodus could be yet another sign that Apple is scaling back its automotive ambitions after the company originally planned to build its own car from the ground up.

Apple’s self-driving car project

After plans to build its own car were scraped, Apple is now rumored to be working on autonomous driving platforms that could be used in third-party vehicles. The company may still choose to design and manufacture its own car in the future, but that’s looking less likely ever since Apple veteran Bob Mansfield took over the project last year.

The group of engineers that defected to Zoox supposedly included experts in both autonomous driving as well as traditional systems like braking and suspension. Apple’s new requirements left many of the engineers sidelined and they were eventually hired one-by-one by Zoox over the last few months.

Apple’s car project team has allegedly morphed into the creation of a self-driving shuttle bus for employees. Zoox, on the other hand, is developing an entire fleet self-driving cars. The company has also hired away a number of Apple supply chain specialists over the last few years.