OREM — A private Web site that maps the known residences of Utah's registered sex offenders has raised an alarming concern — the state may have incorrect addresses for as many as two-thirds of those listed on the registry.

That means the state may not know the whereabouts of as many as 5,400 of its roughly 8,200 registered sex offenders.

Mark Olsen, an account manager for Orbizon, the Orem-based Web development company that designed the site — www.mapsexoffenders.com — said the Utah Department of Corrections, which maintains the information on the registry, contacted his company Monday and told it about the potentially incorrect information.

"We were concerned about that, so we turned off our Web site," Olsen said.

Messages left with Jack Ford, a Utah Department of Corrections spokesman, were not returned.

A federal statute known as Megan's Law requires each state to maintain a registry listing the names, addresses and crimes of convicted sex offenders and to notify the public any time the offenders move. The specific information gathered and the way it is disseminated is left up to the individual states.

The UDC's handling of the sex offender registry has also raised concern with a national group, Parents for Megan's Law, that monitors the way states maintain their sex offender registries.

Parents for Megan's Law regularly surveys agencies that are responsible for the registries in each state to measure their compliance with the federal statute. In the most recent survey, Utah received a zero.

"Utah, after numerous requests, refused to give us the information, so they get a zero," said Laura Ahearn, the executive director of Parents for Megan's Law. "We've had positive responses from every agency in the nation that administers Megan's Law except the Utah Department of Corrections."

Ahearn said she did not know the reason for UDC's refusal to cooperate. She said it could be a lack of personnel, a lack of resources or bureaucratic red tape. But she did say her organization has sent numerous surveys, by mail and fax, and has never received a response.

"It's very disturbing," she said. "I'm not exactly sure how to interpret it. But if I were in Utah, I would question that."

For now, the question that seems to concern most Utah residents is when Orbizon's site, which was averaging between 15,000 and 30,000 hits per day since it launched last week, will return.

"We've heard from the public, 'Don't shut it down, we love you guys, when are you going to come back?' " Olsen said.