The New York Police Department is playing a recording of Avonte Oquendo's mother's voice out of emergency response vehicles hoping that the 14-year-old autistic teen who's nonverbal will hear it as the search for him nears its second week.

"Hi Avonte, it's mom," Vanessa Fontaine, 48, says in the recording. "Come to the flashing lights Avonte." 

Police, family and friends have been frantically searching for Avonte since he walked away from Center Boulevard School in Long Island City, Queens on Oct. 4. Police have checked all 468 subway train stations, where hundreds of searchers have posted photos of Avonte. They have also waded through countless train tunnels and overgrown lots. Police divers have also searched the East River near the school. An anonymous donor has offered $50,000 for the boy's safe return, bringing the total reward to at least $70,000.

He was last seen on school video cameras and by a school safety agent on duty at the front door. Police said they have reviewed the videotape and interviewed the guard who told Avonte to go back upstairs. The videotape shows Avonte walking down the hall, and exiting the school through a side door. The guard, the last person to see him at around 12:45 p.m., isn't under suspicion in the boy's disappearance, the New York Post reports. 

The family’s lawyer, David Perecman, has filed a notice of claim -- the first step in a lawsuit -- against New York City and the city Department of Education, claiming that Avonte should have never been without supervision. The suit claims that Avonte was allowed to walk out of the school and that educators waited too long to notify police that he was missing. According to several media accounts, the school waited an hour before telling Vanessa Fontaine that her son was missing.

“They dropped the ball; there’s no other way to put it,” Daniel Oquendo Sr., Avonte’s father, told the New York Daily News. “He was seen, but nobody did anything!” 

Daniel Oquendo Jr. said that he and other volunteers will resume searching train stations on Thursday in an effort to find his brother. The family told CBS New York that they believe Avonte is alive.

“Maybe if he’s not out on the street, then somebody does have him and I just hope that whoever does have my brother, they just give him up please so we can have him back,” Daniel Oquendo Jr. said.

The reward, advertised by the advocacy group Autism Speaks, is being posted by the law firm of Oquendo family attorney Perecman; Autism Speaks co-founders Suzanne and Bob Wright; Health First, the employer of Avonte’s mother, Vanessa Fontaine; Manhattan law firm Mayerson & Associates; nonprofit private autism school Manhattan Children’s Center; and an anonymous donor.

A Facebook page -- Bring Avonte Home -- has also been set up to spread the word about the autistic teen's disappearance. 

Police said that Avonte was last seen wearing a gray-striped shirt, black jeans and black sneakers. He's 5 feet, 3 inches tall and weighs 125 pounds. Anyone with information should call the NYPD’s Crime Stoppers tipline at 1-800-577-TIPS, or visit the Crime Stoppers website and submit your tip there, or texting your tip to 274637 (CRIMES) and enter TIP577.