Nearly 18,000 door alarms have been installed in New York City schools and another 2,300 will be installed as the school system works to ease safety problems that could arise because of unmonitored doors.

The city's education department is adding the door alarms at more than 1,400 schools citywide as part of Avonte’s Law. The city council enacted the law after Avonte Oquendo, a 14-year-old boy with autism, walked out of his school through an unattended door in 2013 and disappeared. He was found dead three months later.

The law directs the city’s school system to evaluate the exterior doors in all its elementary and special-needs schools to determine which ones should be equipped with alarms, so school personnel can be alerted and react when someone is opening a door without authorization.

NBC New York reports that installation of the alarms, mandated by a law enacted last year, is scheduled to be completed by later this fall.

Video from NBC New York: