Federal auto safety regulators opened an investigation Tuesday into a possible defect in Tesla door handles that have reportedly left parents unable to reach into back seats to get their children out of the cars. The National Highway Traffic Safety Administration said that its preliminary evaluation is for the 2021 Tesla Model Y. The agency said that the electronic door handles of the vehicle may become inoperative due to low battery voltage and impede vehicle reentry and leave passengers trapped inside. The agency said it received four reports of parents breaking windows to remove a child. The investigation covers approximately 174,300 of the midsize SUVs.