New York (CNN) -- The mother of a teen with autism who went missing three weeks ago declared Friday, "My son, he is alive." Her comments followed the police commissioner's assessment that the department was "not hopeful" of finding 14-year-old Avonte Oquendo alive.
"My thoughts are that my son is still out there and I want everyone to continue to help me search for my son. He is not gone," Vanessa Fontaine said Friday at a press conference outside of the school in Long Island City where her son ran away October 4.
Sniffer dogs, video cameras, a search of the sewer system, missing-persons posters and fliers filling the streets, subway alerts and messages in city newspapers, and divers with sonar -- none of it has led officers to Avonte.
"Obviously we have devoted a tremendous amount of resources to the search," Police Commissioner Ray Kelly told CNN affiliate WABC on Thursday. "Unfortunately, we are not hopeful that we're going to find this young man alive, but we are continuing our search."
Fontaine wants police to try new tactics in their search.
"I don't know what the commissioner was thinking of last night by saying that, but my son, he is alive, he is out there ...it's just that we are not looking in the right places," Fontaine told reporters.
Avonte was last seen on surveillance video running out of Center Boulevard School. Three hours later, bloodhounds traced his scent to a marsh near his school, but lost the trail, a source close to the investigation said.
An hour later, the bloodhounds picked up his scent again, this time at a nearby subway station, the source said.
Avonte is fascinated by trains, his family has said. The New York Police Department has focused its search on rail yards, train stations, tracks and tunnels.
All 468 New York City subway stations have been searched, and aviation, harbor and canine units have periodically helped, the NYPD said. Announcements have been made in subway stations urging commuters to keep an eye out for the missing boy.
A mother's worries
Fontaine told CNN's "Piers Morgan Live" last week that she believed her son was alive and that someone may have been 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 to let him go."
A reward of $77,500 has been offered for his safe return.
Police said Avonte was last seen wearing a gray striped shirt, black jeans and black sneakers. He is 5 feet, 3 inches tall and weighs 125 pounds.