WASHINGTON (Reuters) -Tesla told U.S. regulators that its answers to questions on the safety of its robotaxi deployment in Texas are confidential business information and should not be made public, according to a letter released on Monday.

On Friday, the National Highway Traffic Safety Administration said it was reviewing answers given in response to the agency's questions about the safety of its self-driving robotaxi in poor weather among numerous issues.

The agency said on Monday that Tesla was invoking a federal law that "restricts NHTSA's ability to publicly release what the companies label as confidential." The agency added that "following an assessment of these responses and other relevant information, NHTSA will take any necessary actions to protect road safety."

NHTSA has been investigating since October collisions of Tesla vehicles using Full Self-Driving software under conditions of reduced visibility. The probe covers 2.4 million Tesla vehicles equipped with FSD technology after four reported collisions, including a 2023 fatal crash.

NHTSA noted on Monday that "the agency's investigation into Tesla's FSD-Supervised/Beta remains open."

Tesla said the information it submitted to NHTSA is commercially valuable because competitors could use it to improve their own advanced driver assistance and automated driving systems.

"Nefarious actors could also use the marked information to smear Tesla's brand for the sake of notoriety," Tesla regulatory senior counsel Casey Blaine wrote in the letter to the NHTSA. "Absent public disclosure, access to the marked information and all of the knowledge gained from it would require significant expenditure of time and resources and very intimate knowledge about Tesla."

On Sunday, Tesla deployed a small group of self-driving taxis picking up paying passengers in Austin, Texas, with CEO Elon Musk announcing what he called the robotaxi launch and social-media influencers posting videos of their first rides.

The event marked the first time Tesla cars without human drivers have carried paying riders, a business that Musk sees as crucial to the EV maker's financial future.

Tesla shares were up 8% at $347.80 on Monday afternoon.