Authorities filed state and federal charges against 20 people for possession and distribution of child pornography as the result of a 30-day effort targeting online child predators, U.S. Attorney Karen Hewitt said Friday in San Diego.

Nineteen of the defendants are San Diego County residents living in the Del Mar, El Cajon, La Mesa, Oceanside, San Diego. One man lives in El Centro, Calif., and another is from Annandale, N.J. Hewitt released a list of their names and the charges against each one.

Pornographic and sexually explicit images seized during "Operation Artemis'' included an infant and toddlers being sexually abused and adults having anal sex with children, Hewitt said.

Some of the people arrested were charged with enticing minors to pose naked for photos, which were later posted on the Internet, the prosecutor said.

The investigation was spearheaded by the San Diego Internet Crimes Against Children Task Force, whose members include the District Attorney's Office, U.S. Immigration and Customs Enforcement and other law enforcement agencies.

"We are all united in our efforts to protect children,'' Hewitt said.

San Diego police Chief William Lansdowne said the sweep serves as a fair warning to online sexual predators.

"We're going to come after you,'' Lansdowne said.

A registered sex offender was among those arrested, said ICE Acting Special Agent-in-Charge Joe Garcia.

The defendants include a grocery store clerk, real estate manager and sales consultant, he said.

The operation -- which took place during the month of March -- was intended to send a clear message: "The Internet is not the Wild West,'' Garcia said.

Hewitt said the crimes occurred across multiple jurisdictions, with some child pornography produced overseas.

"It's reprehensible, and we're not going to stand for it,'' Hewitt said. "To us, it's about protecting kids.''

The defendants face anywhere from 37 months to 15 years in prison if convicted, depending on the number of images involved, the prosecutor said.

District Attorney Bonnie Dumanis said parents should be aware of what their children are viewing, noting that computers used by kids should be in a central location and not in children's bedrooms.