04/19/2012 at 06:50 PM EDT
He was the first milk carton child.
Six-year-old Etan Patz's disappearance in 1979 made headlines and inspired the movement to draw attention to missing children.
President Reagan named May 25 – the day Etan vanished on his way to a New York bus stop – National Missing Children's Day, and the milk carton campaign was born.
But young Etan was never found, and the case was largely forgotten by the public.
Now, more than three decades later, authorities have re-launched their search, tearing out drywall and shelves from the basement of a commercial building near the bus stop where Etan was believed to have been headed.
"We're looking for human remains, clothing or other personal effects of Etan Patz," police spokesman Paul Browne says. "It's a very painstaking process."
Although police are not saying what reignited the case, law enforcement sources tell CNN
a cadaver dog picked up a scent in the building.
The disappearance had triggered a massive manhunt involving hundreds of law enforcement personnel and bloodhounds, but no sign of Etan was ever detected.
"We hope we will be able to bring closure to the investigation and family," says FBI spokesman Tim Flannelly, according to the New York Daily News.
"We are committed to this case, and despite the fact that a disappearance occurred in 1979, we are here today doing the best we can."