Shares of Tesla rose sharply on Monday, their best day since March 2021, after the electric carmaker passed a significant milestone to roll out its advanced driver-assistance technology in China.

The company's share price closed up 15% as investors reacted to news surrounding Tesla CEO Elon Musk's visit to China.

Tesla on Sunday said local Chinese authorities removed restrictions on its cars after passing the country's data security requirements.

The move raised expectations that Tesla's driver-assistance software Full Self-Driving, or FSD, would soon be available in the country, which is the largest market for electric vehicles.

While Tesla's electric cars are some of the most popular vehicles in China, they have reportedly been banned from some government-related properties due to data security concerns.

Separately, the Biden administration earlier this year announced a probe into whether imported cars from China pose national security risks due to their ability to potentially collect sensitive data.

FSD is an upgrade to Tesla's Autopilot driver assistant. Tesla has offered its FSD technology in China for years, but with a restricted feature set that limits it to operations, such as automated lane changing.

Tesla does not yet make or sell cars capable of full autonomous driving. It sells "Level 2" driver-assistance systems, marketed under the brand name FSD.

Musk's company has been sued in the U.S. by the California Department of Motor Vehicles for false advertising with its Autopilot and Full Self-Driving driver-assistance systems.

Tesla responded that the DMV had been aware of its use of these brand names for years and chose not to take action. The firm believes Californian law on advertising of autonomous driving systems violates free speech.