That means some people convicted of things like rape and sexually abusing children in other states are living in the Triangle and a search of North Carolina's sex offender registry doesn't show them.
Reem Baloch made that discovery about a man she lived with for two years and had a child with.
"I got up and I started yelling and just horrified and scared," she recalled.
She says she met Rob Fish on the internet in September, 2001 when he moved to Raleigh. It wasn't until earlier this year while in the midst of a custody battle that she discovered his past. She had checked the state registry for sex offenders multiple times in the past, but that day she did something different.
"I have a feeling in my heart that there's something not right about him. And so one day, I went to the national registry," she recalled. "And that's when I discovered it."
She discovered Fish is on the national sex offender registry - with an address in Apex - but he does not appear on the North Carolina sex offender registry.
"No one knows. No one has any idea he's a level 3 registered sex offender," said Baloch.
Fish is not an isolated case. The I-Team discovered 26 sex offenders in Wake County who are on the national registry, but are not required to register in North Carolina. There are five more in Cumberland County and one in Durham.
How does it happen? Under state law, sex offenders who were convicted or released from prison before 1996 and moved to North Carolina before December 2006 do not need to register in North Carolina.
That means many years sex offenders who committed their crime in another state and then moved here can keep their sex crime a secret.
We took the findings of our investigation to State Representative Tim Moore -- who co-sponsored previous sex offender laws.
"First of all, thank you for doing this story because it's bringing to the attention of legislators something that we need to look at," he said. "It's my intent to come back and file a bill to fix this loophole we have."
Also during our investigation, we discovered the majority of sex offenders listed on the national registry have only a city with their information - so it's not clear exactly what neighborhood they live in.
Baloch told ABC11 she was shocked that it took an I-Team investigation to bring the issue to the attention of lawmakers.
"I mean it's ridiculous. It should not happen. And that's why there's future victims out there because people can't keep their children safe, because they have no way of knowing," she offered.
The I-Team contacted Rob Fish for comment on this story. He declined.