A total of 72 individuals were charged for their participation in an international criminal network dedicated to child sexual abuse, U.S. Attorney General Eric Holder and Department of Homeland Security (DHS) Secretary Janet Napolitano announced.

To date, 52 of the 72 charged defendants have been arrested in the United States and abroad, 20 remain at large, the Justice Department said in a statement.

The prosecutions, the largest to date in the U.S. of individuals who participated in online child pornography, were results of the Operation Delego, an ongoing investigation that was launched in December 2009.

The operation targeted the 72 charged defendants and more than 500 additional individuals around the world for their participation in Dreamboard -- a private, members-only, online bulletin board that was created and operated to promote pedophilia and encourage the sexual abuse of very young children, according to the statement.

"The members of this criminal network shared a demented dream to create the preeminent online community for the promotion of child sexual exploitation but for the children they victimized, this was nothing short of a nightmare," said Holder.

All 72 of the defendants were charged with conspiring to advertise and distribute child pornography, and 50 of them were also charged with engaging in a child pornography enterprise.

Xinhua