The U.S. attorney general called it the worst kind of child pornography case.
U.S. Attorney General Alberto Gonzales said in a news conference that undercover investigators infiltrated an international Internet chat room as part of the probe.
On Wednesday in Chicago, Gonzales announced 27 child pornography indictments.
The arrest list includes 40-year-old Lisa Winebrenner from Osceola.
She's accused of acting as a private chat room gatekeeper, where invited users traded child porn pictures and video, including live streaming video of child molestations.
The ring operated through MSN.com and Yahoo.com online chat rooms, as well as private chat rooms set up through independent software, according to investigators.
"The behavior in these chat rooms and the images many of these defendants sent around the world through peer-to-peer file sharing programs and private instant messaging services are the worst imaginable forms of child pornography," Gonzales said at a news conference.
At the Des Moines Federal Building, agents with U.S. Immigration and Customs Enforcement were part of the investigation.
Local agents would not go into detail about the case, but they said it's one of at least a dozen child porn cases the office takes on a year.
Agents seek materials online and seize computer hard drives and discs.
"It's very difficult to be involved in that kind of investigation because children are involved, and they are exposed to things that we normally wouldn't see, but a lot of the agents do it because they feel it's something that needs to be done," said Estela Biesemeyer, the resident agent in charge.
Federal agents arrested Winebrenner at home Tuesday in Osceola. They took her to Chicago, and she appeared in front of a federal judge Wednesday.
Authorities said that just before Winebrenner's arrest, she used a computer program called Evidence Eliminator on her hard drive.
She's accused of child porn conspiracy.
