Chicago ? Participants in an international Internet chat room transmitted live visuals of child molestation and traded thousands of pictures of child pornography, federal authorities said Wednesday in announcing charges against 27 people.

U.S. and international authorities have charged 27 people who took part in the Kiddypics & Kiddyvids chat room. The youngest child seen in pictures or video was less than 18 months old, Atty. Gen. Alberto Gonzales said in announcing the results of the 10-month investigation.

The defendants include Brian A. Annoreno, of Chicago, who prosecutors say molested an infant and transmitted it live to a viewer in the Canadian city of Edmonton.

“The behavior in the chat room and the images sent around the world … are the worst imaginable form of child pornography,” Gonzales said at a news conference in Chicago.

Investigators identified seven children who were molested on the streaming video, Gonzales said. Four molesters are among those charged, prosecutors said.

U.S. Immigration and Customs Enforcement, a unit of the Homeland Security Department, led the U.S. investigation.