Apple's autonomous car project is sucking resources and key employees away from other departments, just as the Watch did when staff described the wearable as a "black hole" for resources last year.

The demand on resources has led senior managers to complain about their talented staff being moved away to focus on the car project, according to "sources familiar with the matter" speaking to The Register.

In early 2014, Apple CEO Tim Cook gave the green light for design vice president Steve Zadesky to lead a group of up to 1,000 employees from different parts of the company to work on a vehicle, sources for the Wall Street Journal claim. Unmarked buildings leased by Apple and containing garage space have since been spotted close to its California headquarters.

Zadesky worked as an engineer at Ford between 1996 and 1999 before joining Apple, where he helped create the iPod and iPhone. In 2014, Apple hired industrial designer Marc Newson, close friend of Apple's head of design Jony Ive and the creator of a 1999 Ford concept car, the 021C.

More than just car software

At first dismissed as research into CarPlay, Apple's software link between cars and iPhones, the project started to become more believable in early 2015, as Apple hired a number of automotive designers and vehicle dynamics engineers. This, plus the seniority of Apple executives involved, suggests Titan is more than just a software service, claims the Financial Times.

Project Titan has already caused a number of Tesla employees to "jump ship" to work at Apple, according to an email claiming to be from an Apple employee. Sent to Business Insider, the email said: "Apple's latest project is too exciting to pass up. I think it will change the landscape and give Tesla a run for its money."

A mystery van spotted driving around San Francisco with autonomous driving kit such as roof-mounted cameras and sensors was at first seen as proof Apple was working on a car, but these vans have since been revealed to be used by Apple to build a mapping application to rival Google Street View.