(CNN) -- The search of a New York City basement for possible clues in the disappearance of 6-year-old Etan Patz more than three decades ago has ended, with no human remains found, a source briefed on the investigation told CNN Monday. A field test on what was considered a possible blood stain found in the basement was negative, the source said. The stain, some possible strands of hair, and a piece of paper found in the search will be analyzed at an FBI laboratory in Quantico, Virginia, the source said.