ENGLEWOOD, N.J. (CBSNewYork) — The New Jersey sex offender registry says dozens of people charged with sex crimes are unaccounted for.

According to New Jersey State Police, there are about 4,300 people convicted of sex crimes on the registered sex offenders list, as part of Megan’s Law. Now, 71 throughout the state have fallen off the radar of local police, CBS2’s Magdalena Doris reported.

“I would be terrified when I get to know that my kid is around, or these people are around my kid,” said Shruti Valid of Hackensack.

According to Megan’s Law in New Jersey, sex offenders are required to register for life. Some must check in every 90 days, others annually.

Offenders who do not update their whereabouts are classified as “non-compliant.”

“So how are they trying to track them down?” said Robin from Englewood.

The task falls into the hands of local police and prosecutors. CBS2 spoke to former Bergen County Prosecutor John Molinelli.

“They have some pretty sophisticated computer software — mapping software — that helps them keep constant track of the Tier 1, Tier 2 and Tier 3 offenders,” Molinelli said.

The tiers are determined by the severity of the crime, with Tier 3 being the most severe. Molinelli said many on the “non-compliant” list are often Tier 1 offenders, who move and forget to reach out to local police.

He said a greater threat to the public would warrant swift action.

“If there was a Megan’s Law offender in Tier 3 that was absent, the local chief would certainly notify the community,” Molinelli said.

But those who work with sex abuse survivors said said no matter what level or tier offenders fall under, the fact that some are unaccounted for is traumatic.

“Knowing that the person who attacked them is accounted for gives them a peace of mind in terms safety and their well-being,” said Helen Archnotou of the YWCA of Bergen County. “So not knowing where they are, obviously, does the exact opposite of that.”

The two New Jersey counties with the most unaccounted for sex offenders are Passaic and Union, with 13 each.

The problem is not only seen in New Jersey, CBS2’s Valerie Castro reported. New York state has more than 23,000 sex offenders on its registry at high risk of reoffending, and the whereabouts of 228 of them are unknown.