US auto safety regulators opened an investigation into whether some Tesla Inc. vehicle doors are defective, citing incidents in which exterior handles stopped working and trapped children inside. The National Highway Traffic Safety Administration said Tuesday it’s opening a preliminary evaluation of Tesla’s electrically powered door handles becoming inoperative due to issues with certain vehicles’ low-voltage batteries. While the probe specifically focuses on an estimated 174,290 Model Y SUVs, the regulator said the investigation could widen.