Pony.ai, an autonomous vehicle startup based in Silicon Valley and Guangzhou, China, is no longer able to test its vehicles in California after the state’s Department of Motor Vehicles revoked the company’s license for “numerous” safety violations. The news was first reported by TechCrunch.

The issue is that the company’s workforce of safety drivers are not very safe drivers. The DMV said that, while reviewing Pony.ai’s testing license, it found “numerous violations” on the driving records of the company’s safety drivers. Pony.ai currently has 41 autonomous vehicles and 71 safety drivers registered on its permit in California.

“Because of the critical role of safety drivers to facilitate the safe testing of autonomous technology and the need for these drivers to have a clean driving record as established by the DMV’s autonomous vehicle regulations, the DMV is revoking the permit, effective immediately,” a DMV spokesperson said.

This isn’t the first time that Poiny.ai has run afoul of the California DMV, a state agency that manages one of the largest AV testing programs in the country. Last year, the company’s permit to test driverless vehicles — autonomous vehicles without safety drivers — was suspended after a reported vehicle collision in Fremont, California.

A spokesperson for Pony.ai said the DMV revoked the permit because three of its safety drivers had problematic driving records. “Pony.ai approaches the development of autonomous vehicle technology with safety as our foundation, and we are proud of our safety record,” the spokesperson said in an email. “Pony.ai has driven over 6.8 million real-world autonomous miles, in which no injuries have occurred.”

This represents a serious hurdle to Pony’s commercial plans in the state. Shortly after receiving its driverless testing permit last year, Pony.ai founder and CEO James Peng told The Verge that the company was also seeking approval to include those vehicles in its robotaxi service in California. “We are actually at the final stage of getting the approval for travelers,” he said.

Pony.ai was valued at $3 billion after a $400 million investment from Toyota last year. The company has been testing autonomous vehicles in the Chinese cities of Beijing and Guangzhou since late 2018 as well as in Fremont and Irvine in California. Pony recently received a permit to operate its autonomous taxi service in China, making it the first company to win the country’s approval.