The woman urges her 14-year-old son, identified as Avonte, to walk toward flashing blue-and-white lights of the emergency vehicles that have been searching for him, CNN reported Friday.
"Avonte, this is your mother. You are safe. Walk toward the lights," Vanessa Fontaine's recorded message repeats.
The recording is part of the New York Police Department's search to find the youth, last seen on surveillance video running out of Center Boulevard School in Long Island City Oct. 4, Keith Brooks, director of operations for CityWide Disaster Services, said Thursday.
Officials said they hope the teen, who can't communicate verbally, will hear his mother's voice and approach the emergency vehicles.
A reward fund for the safe return of Avonte grew this week to $77,500, CNN said.
Fontaine told CNN she believes her son is alive and that someone is probably holding him.
"My message to my son is that I love him and we're going to find him," she said. "You'll come home to your family. And for anyone who has him, please be kind and ... let him go."
New York Police Commissioner Ray Kelly said he didn't hold the school safety officer on duty when the teen left responsible for the boy's disappearance. Kelly said the safety officer told Avonte to go back upstairs when he approached the front door; surveillance video showed Avonte heading down another hallway and exiting the building from a side door.
Surveillance video provided by the police department shows the teen wasn't stopped when he exited the school.
"Even though he's 14, it shouldn't matter," Fontaine told CNN. "No one should be, you know, allowed to run around the hallways in school. And that security guard should have questioned him."