More evidence about Apple's self-driving car project has come out, suggesting that the company is in search of a place in California's Bay area to test its car.

The Guardian, citing a correspondence obtained by it, reported that Apple is scouting for secure locations in the San Francisco Bay area to test the car, adding that the project appears to be further along than many suspected.

In May, engineers from Apple's Special Project group met with officials from GoMentum Station, a 2,100-acre former naval base near San Francisco that is being converted into a secure testing ground for autonomous vehicles, the newspaper reported.

"We would… like to get an understanding of timing and availability for the space, and how we would need to coordinate around other parties who would be using [it]," Apple engineer Frank Fearon's quoted correspondence read.

Apple wanted to see "a presentation on the… testing grounds with a layout, photos, and a description of how the various areas of the grounds could be used," according to the documents.

"We had to sign a non-disclosure agreement with Apple," Randy Iwasaki, executive director of the Contra Costa Transportation Authority, owner of GoMentum Station, told the newspaper. "We can't tell you anything other than they've come in and they're interested."

The site with barbed wire fences has already been used by Mercedes-Benz and Honda to carry out experiments with self-driving cars.

Apple declined to comment on the revelation.

Although Apple has not officially announced its so-called Titan car project, there has been evidence regarding the same. The company recently hired a number of motoring industry veterans from companies including Ford, Chrysler and Tesla.

The Guardian noted that Apple's self-driving car is apparently almost ready for the road.

Rival companies including Google and Uber are also progressing with the development of robot cars, investing large amounts of money.