Uber UBER.N has committed close to half a billion dollars in self-driving startup Nuro, two sources directly aware of the matter told Reuters, detailing the extent of a major investment by the ride-hailing company in developing commercial robotaxis.

After years of false starts, the robotaxi industry is re-accelerating development, testing and early commercial deployment, led by companies including Tesla TSLA.O, Alphabet's GOOGL.O Waymo and Amazon's AMZN.O Zoox.

Uber has been positioning itself as a platform for the nascent industry and has partnered with many autonomous vehicle companies, including Chinese tech giant Baidu 9888.HK, U.S. electric vehicle maker Rivian RIVN.O, and British startup Wayve. It also is working with Waymo in some U.S. cities.

One of Uber's commitments is a three-way partnership with Nuro and electric vehicle company Lucid LCID.O to roll out 35,000 robotaxis using Lucid's Gravity SUVs and upcoming midsize vehicles, Nuro's technology and Uber's platform.

The size and details of Uber's financial commitment to Nuro have not been reported previously and reveal the full scale of the financial ties binding the firms.

Uber previously had reported investing $500 million in Lucid and planning a multi-hundred-million dollar investment in Nuro, including participating in a $203 million funding round for Nuro that valued the Silicon Valley startup at $6 billion.

Uber has since made an unreported follow-on investment in Nuro significantly larger than its first funding, both the sources said, declining to be named. Uber had also agreed to provide additional funding for Nuro once it hit certain development and commercial milestones, without disclosing terms. Together these commitments tally nearly $500 million.

The first few milestones have already been met on time, triggering the release of some funds from Uber, one of the sources told Reuters.

The remaining money is tied to targets including testing without a driver, planned for later this year, carrying passengers in those driverless cars, expected by the end of this year, and ramping up the service next year, the source said.

Uber and Nuro declined to comment.