When it was discovered that Apple was using a fleet of Lexus RX 450h hybrids for testing its autonomous-car system, it was assumed that Apple didn't buy them direct from Lexus. But now we probably know where they came from.

Apple's small fleet of Lexus hybrids likely came from Hertz's Donlen fleet management subsidiary, Bloomberg reports, citing documents from the California Department of Motor Vehicles, which lists Apple as the lessee and Donlen as the lessor.

The iPhone maker received a permit from the state of California in April, giving it the capability to test its autonomous-vehicle systems on public roads. Apple CEO Tim Cook acknowledged earlier this month that his company intends to develop a system for self-driving cars, rather than a complete car, that could then be sold to actual automakers.

Earlier on Monday, Google's sister company Waymo and Avis Budget Group announced that the latter would be in charge of servicing and housing the former's fleet of self-driving minivans. 

It's unclear if Apple is only leasing these vehicles from Donlen and servicing them elsewhere, or if it's a partnership similar to the Waymo-Avis-Budget arrangement.

Neither Apple nor Hertz Donlen immediately returned requests for comment.