Cooper is one of several state attorneys-general who demanded that MySpace provide data on how many registered sex offenders were using the site along with information about where they lived.
Another attorney-general, Richard Blumenthal of Connecticut, said: "I'm absolutely astonished and appalled because the number has grown so exponentially over so short of time with no explanation."
MySpace declined to comment on the figure, focusing instead on its efforts to clean up its profile rolls.
"We're pleased that we've successfully identified and removed registered sex offenders from our site and hope that other social networking sites follow our lead," Hemanshu Nigam, MySpace's chief security officer, said.
Cooper is pushing for a state law that would require children to receive parental permission before creating social networking profiles, and require the websites to verify the parents' identity and age.
He is also working with law enforcement officials in other states in pressing MySpace to use age and identity verification methods voluntarily.
Based on media reports, Cooper's office found more than 100 criminal incidents this year of adults using MySpace to prey or attempt to prey on children.
Most recently, a Virginia man pleaded guilty Monday to kidnapping and soliciting a 14-year old girl he met on MySpace.
Critics say the proposed restrictions are unconstitutional because they prohibit free speech or impede interstate commerce.
The bill has already passed the North Carolina senate and now goes to a House subcommittee for more consideration.