New York City police are searching for a group of people they say took a subway train on a joyride. The department released images Wednesday of six individuals who they say commandeered an unoccupied “R” train in Queens over the weekend.

It's unclear how they managed to access the cab on the train. MTA Chair and CEO Janno Lieber called the intrusion a "failure" of security that was "not acceptable," and suggested new train car models should lock up operator cabs using biometric sensors instead of traditional locks.