NEW YORK (AP) — Police and the FBI searched a Manhattan basement Thursday for the remains of a 6-year-old boy whose 1979 disappearance on his way to school helped launch a missing children’s movement that put kids’ faces on milk cartons.

Etan Patz vanished on May 25, 1979, after leaving his family’s SoHo apartment for a short walk to catch a school bus. It was the first time his parents had let him go off to school alone.

A forensic team planned to dig up the concrete floor and remove drywall partitions to find blood, clothing or human remains in the building, just down the street from Etan’s home, police spokesman Paul Browne said. The work is expected to take up to five days.

FBI and police officials didn’t publicly announce what led them to the site, but a law enforcement official told The Associated Press that investigators made the decision to dig after an FBI dog detected the scent of human remains at the building over the past few weeks.

Investigators have long eyed the basement with curiosity because it can be accessed from the street on the boy’s route to school. At the time, the space was being used as a workshop by a neighborhood handyman who was thought to have been friendly with Etan.

FBI investigators have interviewed the man several times over the years. Investigators questioned him again recently, and as a result of those discussions decided to refocus their attention on the building, according to the law enforcement official.

The official spoke to the AP on condition of anonymity because the investigation is ongoing. Two other law enforcement officials also confirmed that an FBI dog had indicated the scent of human remains in the space.

Etan’s disappearance drew national attention to child safety, ushered in a generation of parents who became afraid to send their kids out alone and helped fuel a movement to publicize missing children’s cases. Etan’s face was among the first to appear on milk cartons. President Ronald Reagan declared May 25, the day of his disappearance, National Missing Children’s Day.

Etan’s parents, Stanley and Julie Patz, became outspoken advocates for missing children. For years, they refused to change their phone number, in the hope that Etan was alive somewhere, and might call. They never moved, although they obtained a court order in 2001 declaring the boy dead.

Stanley Patz didn’t respond to phone calls and email messages Thursday. A man who answered the buzzer at the family’s apartment said they wouldn’t be speaking to the media.

No one has ever been prosecuted for Etan’s disappearance, but Stanley Patz sued an incarcerated drifter and admitted child-molester, Jose Ramos, who had been dating Etan’s babysitter around the time he disappeared.

Ramos, who is not the carpenter whose workspace was being searched, denied killing the child, but in 2004 a Manhattan civil judge ruled him to be responsible for the death, largely due to his refusal to contest the case.

Ramos is scheduled to be released from prison in Pennsylvania in November, when he finishes serving most of a 20-year-sentence for abusing an 8-year-old boy. His pending freedom is one of the factors that has given new urgency to the case.

Investigators have looked at a long list of possible suspects over the years, and have excavated in other places before without success.

The 13-foot by 62-foot basement space being searched Thursday sits beneath several clothing boutiques. Investigators began by removing drywall partitions so they could get to brick walls that were exposed back in 1979 when the boy disappeared, Browne said.

Browne said the excavation is part of a review of the case, which was reopened by the Manhattan district attorney two years ago.

“This was a shocking case at the time and it hasn’t been resolved,” Browne said.

The law enforcement activity forced the temporary closure of some businesses on the block, including the fashion boutique Wink, on the ground floor of the excavated building.

“It’s insignificant,” owner Stephen Werther said of the lost business. “It’s retail. There’s always another day for us to make a living. This may be the family’s last chance to find out what happened to their son.”

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Associated Press writers David B. Caruso and Colleen Long contributed to this report.