When 6-year-old Etan Patz disappeared from his SoHo neighborhood on May 25, 1979, America was shocked. It was the first day the New York City boy was allowed to walk to the school bus stop alone. Now, 33 years later, a break in the case has prompted the FBI and New York City police to reopen the case and try to find out what happened to Patz.

He was the first missing child to be featured on a milk carton.

Federal and local law enforcement official swooped down on Downtown Manhattan on Thursday to dig up the basement of a SoHo apartment close to Patz's home. Patz was legally declared dead in 2001.

FBI New York Office spokesman Tim Flannelly told NY 1 that the federal agents are executing a search warrant at 127 Prince Street after following leads.

A cadaver dog brought to the building's basement indicated a hit, which could indicate the current or past presence of human remains.

In 1979 the basement, now a clothing store, was the workshop of Othneil Miller, according to Good Morning America, which stated that the local handyman gave Patz $1 for helping him, the night before he disappeared. The basement was searched that year, but officials didn't dig up the floor.

Obviously there is probable cause for us to be here executing this search warrant, Flannelly said.

Investigators are also reexamining claims that the boy was abducted by Jose Ramos, a convicted pedophile and boyfriend of Patz's babysitter.