Heavily funded autonomous driving startup Aurora Innovation Inc. has raised more capital to fuel its product development plans, which it disclosed include building self-driving hydrogen cars.

The investment, announced Wednesday night, is an extension to the $530 million round that Aurora raised in February. It was reported at the time that the startup had a post-money valuation north of $2.5 billion. Aurora said the new cash injection brings the total value of the round to more than $600 million but didn’t share a specific figure.

The additional capital came courtesy of Baillie Gifford & Co. Ltd., a British asset management firm notable for being the largest outside shareholder in Tesla Inc., and Hyundai Motor Group. Sources told TechCrunch that the automaker’s investment was below $30 million.

Besides being an investor, Hyundai is also one of Aurora’s most important partners. The companies launched a collaboration last year with the goal of bringing autonomous vehicles to market by 2021. On occasion of the new funding, they divulged a few details about the previously secretive alliance.

Aurora has spent the past year working with Hyundai to integrate its autonomous driving systems into the automaker’s hydrogen-powered Nexo sport utility vehicle. The companies now plan to expand the scope of the initiative to more models, including some from Hyundai subsidiary Kia Motors Corp. Those unspecified models might include the up to 17 additional hydrogen fuel cell vehicles that the automaker looks to launch by 2025.

Hyundai has big plans for the Aurora-powered cars. The company plans to move into the ride-hailing market by deploying fleets of autonomous taxis in cities worldwide, with the first commercial trials set to begin by 2021.

Hyundai isn’t the only major automaker working with Aurora. Earlier this week,  Fiat Chrysler Automobiles NV teamed up with the startup to integrate its autonomous driving technology into commercial vehicles. Aurora also counts Chinese electric vehicle maker Byton Ltd. as a customer.

Little is known about the startup’s technology except that it’s designed to facilitate so-called Level 4 autonomy. The term describes vehicles that are capable of navigating without any human input whatsoever, but can only do so under favorable driving conditions.

Aurora provides not only the software necessary for autonomous navigation but also related hardware. Last month, the startup bought a Montana firm called Blackmore Sensors and Analytics Inc. that developed lidar systems for self-driving vehicles. Aurora could make more strategic acquisitions in the future if it so chooses: the startup has raised a total of more than $700 million outside funding.

Photo: Aurora Innovation