In an interview with the BBC, Tesla CEO Elon Musk said it is an "open secret" that Apple is developing an electric car. Musk made the statement when asked if he had heard anything about Apple's car development plans and went on to highlight the huge number of hires Apple has made as evidence.

"Well, it's pretty hard to hide something if you hire over a thousand engineers to do it," he said, before adding that he believed Apple was serious about the project. "This is an open secret."

Musk went on to say Tesla welcomes participation by any company that wants to create electric vehicles, but he cautioned that it's "quite hard to do." He brushed off the interviewer's question of whether an Apple car would be a threat to Tesla, and said that he believes Apple will develop a "compelling" electric car because "it seems like the obvious thing to do."

"Tesla will still aspire to make the most compelling electric vehicles, and that would be our goal, while at the same helping other companies to make electric cars as well."

Musk is aware of Apple's hiring efforts because Apple has made an effort to hire former Tesla employees for its car project. The two companies have developed something of a rivalry as they compete for talent, leading Musk to take a jab at Apple in an October interview, saying "If you don't make it at Tesla, you go work at Apple," a statement he later retracted.

The first rumors surrounding Apple's car project, allegedly codenamed "Project Titan," surfaced in early 2015. Since then, Apple has recruited dozens of engineers and researchers from the automotive industry and other car-related fields, poaching employees from companies like Tesla, Ford, GM, Chrysler, Volkswagen, Samsung, and more.

Over the past few months, there's been a growing body of evidence pointing towards work on a car. Apple sought out a secure testing facility for testing electric vehicles in May of 2015, and met with DMV officials to discuss the laws and regulations surrounding self-driving vehicles in California in September. Most recently, Apple registered three auto-related top-level domain names, including apple.car, apple.cars, and apple.auto.

Little is known about Apple's car project, but the company is rumored to be working on an electric vehicle. Rumors have disagreed on the topic of autonomy, but the most recent information suggests that while Apple is exploring self-driving technology, it is a feature that may come in a later version of the Apple Car.