Toyota Motor Corporation announced a recall of 550,007 vehicles after federal regulators flagged a potential safety hazard with the seat-back locking mechanism.

The recall affects 420,771 Highlander and 129,236 Highlander Hybrid vehicles from model years 2021 through 2024, according to a notice filed with the National Highway Traffic Safety Administration.

Regulators said the second-row seat backs “may fail to lock into position during seat back adjustment.” A seat back that is not properly secured may fail to restrain passengers adequately, raising the risk of injury in a crash at higher speeds.

Toyota will notify all affected owners and direct them to return their vehicles to authorized dealers. Dealers will replace the return springs in the recliner assemblies with upgraded parts free of charge. Owner notification letters are expected to be mailed in April.

This recall follows another recent Toyota action in which approximately 141,000 Prius and Prius Prime vehicles were recalled after it was discovered that rear doors could unexpectedly open while the car was in motion.