Tesla’s Cybercab, a distinctive two-seater without a steering wheel or brake pedals, is set to start picking up members of the public in two states. But the vehicle is already under investigation by the US federal government,

Enthusiasm from fans at the event contrasted with investor concerns about deployment plans and new regulatory questions.

The company says no children under 13 can ride -- even with a parent. That's more restrictive than the Model Y SUVs it's using as robotaxis.

Shares of Tesla ( TSLA) were down nearly 7% in recent trading, making it one of the leading decliners in the S&P 500 and Nasdaq on a down day for broader markets. The move erased much of the stock’s gains earlier in the week.

The National Highway Traffic Safety Administration said it is reviewing the rollout of the vehicle in Austin, Texas, over a self-certification issue.

The National Highway Traffic Safety Administration said it would examine whether the company’s new self-driving taxi, which has no steering wheel, meets federal auto regulations.

NHTSA’s investigation covers an estimated 1,000 Cybercabs, although its unclear whether there are even that many to begin with. Tesla has 45 Cybercabs currently registered with the Texas Department of Motor Vehicles.

Riders in Austin can now hail the two-seater. The company's own July letter says batteries still set the pace.