Robert Moser, a 54-year-old registered sex offender, remained held Friday in the Bergen County Jail following his arrest the day before.
Nutley police were investigating a separate case when they learned of the alleged assaults, which continued until the girl was 12, Acting Bergen County Prosecutor Dennis Calo said.
They contacted their colleagues in Fairview, who alerted Calo's Special Victims Unit.
Moser is charged with two counts of sexual assault by contact with a victim under 13 and a child endangerment offense.
He remained held pending a hearing in Central Judicial Processing Court in Hackensack.
No information was immediately available on Moser's previous conviction.
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