The 44-year-old woman was discovered on Thursday by members of the state police street gang unit as they searched the Paterson home of 42-year-old Michael Mendez, believed to be a member of the Latin Kings street gang.
State police spokesman acting Sgt. 1st Class Brian Polite said based on interviews and evidence, investigators believe the woman was kept in the bedroom for extended periods of time for the last two years and possibly up to 10 years.
Investigators said the woman was sometimes let out of the room when her boyfriend was home.
A neighbor said he has known Mendez for about a dozen years and that Mendez was a familiar face around the three-story brick complex where he lived. He said Mendez often could be seen outside, polishing a car and listening to music.
The neighbor said he saw the woman a few times in recent years, though it was rare. The man, who refused to give his name because of worries over safety, said he remembered seeing the woman get into a car sometime in the last few years.
Neighbors on either side of Mendez's top-floor apartment said they weren't aware that another person lived in the apartment.
"I didn't see any woman," said a man who identified himself only as Buddy and opened his door only a few inches as he spoke. "This is the first I'm hearing of it."
A maintenance worker, who declined to give his name also because of concerns over his safety, remembered the woman "cussing me out one time when I was doing my work."
Mendez, who police say is a member of the Latin Kings, was being held Monday at Passaic County Jail. Authorities didn't know if he had an attorney. No one answered when a reporter knocked on his apartment door Monday.
Mendez was charged with kidnapping, false imprisonment and other counts, including some related to the drugs officials said they were looking for in the first place. State police said they found 4,200 prescription pills valued at $100,000, 190 grams of marijuana valued at nearly $2,000 and nearly $23,000 in cash inside his apartment.
According to court records, Mendez has two prior convictions for aggravated assault, one of which carried a three-month jail term.
The woman was receiving a medical evaluation Monday.