Tesla’s Cybercabs are now in service, but almost immediately after they hit the streets of Austin, Texas, they were under federal investigation. The National Highway Traffic Safety Administration (NHTSA) has begun a probe that covers around 1,000 of the vehicles.

The agency said in a notice that Tesla began commercial service of the Cybercab with a small number of vehicles on Thursday after self-certifying that they’re compliant with all relevant Federal Motor Vehicle Safety Standards (FMVSS). The company indicated that it plans to expand Cybercab operations with more vehicles and in additional locations.

“The vehicles lack permanently attached, conventional manual controls, such as a brake pedal, gas pedal, steering wheel and mirrors,” the agency said. “NHTSA is opening this [audit query] to examine the process and technical data on which Tesla relied when certifying the Cybercab and related issues. Among other things, NHTSA will consider the extent to which Tesla’s certification depended on determinations that certain FMVSS are inapplicable to the Cybercab.”

According to Reuters, Tesla has registered 420 autonomous vehicles in Texas, 45 of which are Cybercabs. It’s not clear how many of the latter are actually ferrying customers to their destinations and how many are used for testing. Tesla is also offering robotaxi rides in Dallas, Houston, Miami, Orlando and Tampa using Model Y vehicles.