The FBI and Manhattan District Attorney's Office are looking at other possible suspects in the Patz case and now have a person of interest.
Members of the FBI and NYPD are searching a building at the intersection of Prince and Wooster Streets Thursday. The search is expected to take several days.
"It's a joint FBI, NYPD search for human remains, clothing or personal effects," said NYPD Deputy Commissioner for Public Information Paul Brown.
The search is linked to new leads in the Etan Patz case. The building is near the spot where Patz, then 6, disappeared on May 25, 1979.
Federal sources told ABC News that the night before Patz disappeared he had been in the basement of 127 B Prince Street, where just prior to today's search a law enforcement cadaver dog got a hit that could indicate the current or past presence of human remains.
According to sources the area of the basement where the dog picked up the scent appears to be one that had been resurfaced with fresh concrete at or shortly after the time of Patz disappearance.
A carpenter or handyman named Othniel Miller who worked in the basement had befriended the 6-year-old boy, multiple sources said. He is now being called a person of interest in the case.
The basement is a 15 by 30 concrete floored room that was last searched by authorities in 1979. At the time, no evidence was found connected to the disappearance of Patz, who was last seen heading to school for the first time unaccompanied by a parent.
Since then drywall has been put up over the brick walls. Authorities said that the dry wall will be removed, the brick examined and tested for blood evidence. Then they will be dug through. The floor will also be dug up in a search for human remains, clothing or other evidence.
The disappearance of Etan Patz helped spark the missing children's movement. Patz was the first missing child ever featured on the side of a milk carton.
He was legally declared dead in 2001. Sources said the suspected killer has long been in jail on other sex crime charges, but in the past prosecutors never felt they had enough to take Jose Ramos to court on the Patz case, one of the most famous of missing children cases in US and one that tugged heart strings.
Manhattan District Attorney Cy Vance re-opened the case after taking office in 2010.
Law enforcement officials tell ABC News that prosecutors are now skeptical whether Ramos did in fact commit the crime. Ramos has never confessed.
Ramos is scheduled to be released from prison in Pennsylvania this year, when he finishes serving 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 after so long. He is not the carpenter whose old workspace was being searched.
Investigators have looked at a long list of possible suspects over the years, and have excavated in other places before without success.
Stanley Patz didn't respond to phone calls and email messages Thursday. A man who answered the buzzer at the family's apartment, just a few doors down from the building being searched, said they wouldn't be speaking to the media.
Get Eyewitness News Delivered