Founder, Chairman, CEO and President of Amazon Jeff Bezos gives a thumbs up as he speaks during an event about Blue Origin's space exploration plans in Washington, U.S., May 9, 2019.

At an all-hands staff meeting in March, Amazon CEO Jeff Bezos told employees that he's fascinated by the recent developments in the auto industry, adding that it was one of the main reasons why Amazon led a $700 million investment in electric vehicle start-up Rivian in February.

"If you think about the auto industry right now, there's so many things going on with Uber-ization, electrification, the connected car — so it's a fascinating industry," Bezos said according to a recording of the meeting CNBC has heard. "It's going to be something very interesting to watch and participate in, and I'm very excited about that whole industry."

Bezos' comments give a rare glimpse into his interest in the auto industry, which Amazon entered in February through its investments in Rivian and another self-driving tech start-up, Aurora. Investing in autonomous technology could eventually help Amazon offer faster and cheaper delivery, as well as automation in other areas, like its cashier-free grocery stores.

Rivian is best known for its electric trucks and has raised $1.4 billion in funding so far, including $500 million from Ford in April. Aurora, a self-driving tech start-up run by former Uber, Google and Tesla executives, is now reportedly worth more than $2 billion following its $530 million funding round in February.

Following those two investments, Amazon's ownership stake in private companies shot up to almost $1.4 billion last quarter, marking the first time it crossed the $1 billion mark since disclosing that figure in 2015. That's up by almost $1 billion from the previous quarter, and roughly five times more than what it owned just two years ago, filings show.

Amazon doesn't break out individual investment amounts, but discloses the total value of its equity and equity warrant investments in both public and private companies.

Amazon did not respond to a request for comment.