Washington ? Prostitution rings from New York to Hawaii forced more than 30 children as young as 12 to have sex at truck stops, hotels and brothels, Atty. Gen. Alberto Gonzales said Friday, announcing a government crackdown.

Nineteen people have been arrested among 31 who have been indicted for sexual trafficking in children, taking minors across state lines for prostitution and other crimes, Gonzales said.

The indictments, in Michigan, New Jersey and Pennsylvania, target the purported operators of four child prostitution rings. Some of the children had been reported missing or had run away because they had been abused at home, FBI assistant director Chris Swecker said.

The heightened federal interest in stopping child prostitution is critical because pimps frequently take children from one state to another, making it more difficult for local police to stop them, said John Rabun, vice president of the National Center for Missing and Exploited Children.