Federal safety regulators said they are investigating whether Tesla’s massive recall in December of essentially all of its vehicles on US roads was sufficient to fix the safety threat of its “Autopilot” feature.

The National Highway Traffic Safety Administration said it has concerns about changes Tesla made to the driver assistance system as part of a December recall.

Federal transportation agency finds Tesla’s claims about feature don’t match their findings and opens second investigation

U.S. auto safety regulators said on Friday they have opened an investigation into whether Tesla's recall of more than 2 million vehicles announced in December to install new Autopilot safeguards is adequate following a series of crashes.

NHTSA launches new probe into adequacy of 2-million vehicle recall in December, after discovering more crashes linked to the controversial technology.

The National Highway Traffic Safety Administration is closing an investigation into the autopilot controls on certain Tesla models, while at the same time opening a new probe into the car maker's fix of the problem.

Two U.S. senators on Friday urged regulators to bar Tesla from allowing the use of driver assistance system Autopilot on roads where it is not intended.