WASHINGTON (BLOOMBERG) - United States safety regulators have a message for Tesla owners intending to use their children to test automated-driving technology: Don't.

The National Highway Traffic Safety Administration said it uses controlled procedures and "it could be highly dangerous for anyone to attempt to test vehicle technologies on their own".

The statement comes in response to recent Twitter posts from Tesla owners appearing to show a child used in a test of a vehicle's so-called Full Self Driving mode.

"No one should risk their life, or the life of anyone else, to test the performance of vehicle technology," the agency said.

"Consumers should never attempt to create their own test scenarios or use real people, and especially children, to test the performance of vehicle technology."

Tesla, which has disbanded its media relations department, did not respond to a request for comment.

The Twitter posts feature a 10-minute video showing the interior of a Tesla vehicle parked on a residential street as the occupant tests the self-driving mode. At one point, a child is shown standing in the street as the vehicle begins moving slowly and then comes to a stop before reaching the child.

The video came after another earlier this month that showed a Tesla car running over child-sized mannequins.

Automated-driving technology has come under scrutiny, particularly after the National Highway Traffic Safety Administration last year started an investigation into whether Tesla's Autopilot is defective.

The probe, which was launched after a dozen collisions at crash scenes involving first-responder vehicles, signalled a change in regulatory posture towards Tesla after years of complaints from safety advocates about the company's marketing of its driver-assistance systems as Autopilot and Full Self Driving.

In its statement on Wednesday, the National Highway Traffic Safety Administration repeated its refrain that "no vehicle available for purchase today is capable of driving itself".

The agency also said on Wednesday that it owns a 2017 Tesla Model S 90D that received a Full Self Driving Beta software update on April 1.

The confirmation sheds new light on its testing capabilities after documents posted online showed the agency had requested the update in January.

In response, Tesla Chief Executive Officer Elon Musk posted on Twitter on Tuesday: "OK we'll turn it on".

The agency said the car is one of a number of vehicles it owns for testing purposes and is currently being used at its facility in East Liberty, Ohio.