"We're not facing an epidemic of girls gone wild," Office of Juvenile Justice and Delinquency Prevention Administrator J. Robert Flores says.

The office, which sponsors research to guide federal juvenile-justice issues, spent $2.5 million on the Girls Study Group, the first U.S.-funded effort to explore girl delinquency, USA Today reports.

"We want to dispel that myth" that violence among girls has increased, the newspaper quotes Girls Study Group leader Stephanie Hawkins of the independent RTI International research group as saying.

The research comes at a time when widely played videos on the Internet show girls beating each other up, the newspaper notes.

Among the findings, which cover 1998 to 2007: 13 percent fewer girls were arrested for all violent crimes, but 10 percent more girls were arrested for simple assault, although the increase occurred before 2004.

Psychology professor James Garbarino of Loyola University, author of "See Jane Hit: Why Girls Are Growing More Violent and What We Can Do About It," questions the study group's data.

Girls underestimate their own violence and FBI data fluctuate depending on policy and demographic changes, he tells USA Today.

Cultural messages tell girls it's OK to be aggressive, he adds.