Authorities have found a suspicious stain on the wall of a basement being searched in the decades-old disappearance of 6-year-old Etan Patz, a source close to the case said Sunday. reported the new clue.

The unknown substance was detected Saturday in a workspace once used by retired handyman Othniel Miller, 75, who was seen with Patz the night before he disappeared from Manhattan's SoHo neighborhood in 1979.

The source also confirmed reports that an unrelated molestation claim led police to reexamine Miller, who is now termed a main person of interest in the Patz case. Miller's ex-wife told law enforcement last year that she divorced her husband in 1986 after learning he had sexually assaulted her 10-year-old niece a few years after Etan disappeared, the source confirmed.

Investigators this week ripped up the basement's concrete floor with jackhammers and saws, and were digging through the dirt in hope of finding the boy's remains after a cadaver-sniffing dog picked up a scent in the 13-by-62-foot basement.

Etan disappeared on May 25, 1979, while walking alone to his school bus stop for the first time, two blocks from his family's home. Miller's workshop was on the route the boy would have taken to his bus stop, authorities said.