A former Los Angeles city fire engineer who allegedly used Internet connections at fire stations to download child pornography was among 11 Southern California men arrested this week and charged with using file-sharing programs to trade child porn.

A Palmdale man, David John Gastelum, 53, was arrested last month after being named in an indictment that charges him with two counts of receiving child pornography and one count of possessing child pornography using the Ares file-sharing system. Gastelum has pleaded not guilty and is scheduled to go on trial Aug. 9.

“Those who trade in child pornography inflict great harm on the most vulnerable in our society by re-victimizing the children in the existing pornography as well as by fueling a market that requires new child victims,” U.S. Attorney Eileen M. Decker said.

“The children depicted in these images that were illegally shared are victimized time and time again,” said Jim Struyk, acting assistant director in charge of the FBI in Los Angeles. “Today’s announcement illustrates the prevalence of this crime, and law enforcement actions should send a message that peer-to-peer networks do not shield criminals from prosecution.”

Charged in Los Angeles federal court were:

—Luis Gutierrez, 49, of Chino, who was previously indicted by a federal grand jury on two counts of receiving child pornography and one count of possessing child pornography. Gutierrez was an engineer with the Los Angeles City Fire Department in 2013 at the time of the alleged offenses, and investigators believe that he used Internet connections at three different fire stations to download the child porn found on his computer;

—Gerald Patrick Beaver, 53, of Cerritos, who was arrested based on law enforcement operations in New Zealand and Oklahoma in which undercover officers allegedly observed him offering to distribute child pornography over the Internet using the Gigatribe file-sharing program. A federal grand jury previously indicted Beaver and charged him with one count of advertising child pornography, two counts of distributing child pornography and one count of possessing child pornography. When a search was executed at Beaver’s home, authorities allegedly found more than 6,000 images and more than 400 videos of child pornography on his computer;

—Jace Jeanes, 39, of Torrance, charged with receipt of child pornography and possession of child pornography that he allegedly obtained using the BitTorrent file-sharing program. Jeanes allegedly possessed more than 20,000 images and videos of child pornography on computer equipment found during a search of his residence;

—Steven David Lavinsky, 58, of Long Beach, charged in a three-count indictment with advertising, distributing and possessing child pornography in a case involving the Gigatribe file-sharing program;

—Kenneth Martin Medellin, 55, of Carson, charged with receipt of child pornography and possession of child pornography using the Limewire file-sharing program;

—Antonio Joseph Garcia II, 41, of Upland, who is charged with four counts of distributing child pornography, one count of receiving child pornography, and two counts of possessing child pornography. In addition to peer-to-peer file sharing, Garcia also allegedly sent and received child pornography by e-mail;

—Michael Brian Perry, 37, of Pasadena, charged in a three-count indictment that accuses him of advertising, distributing and possessing child pornography; and

—Curtis Audun Larssen, 33, of Los Angeles, who is charged with receipt and possession of child pornography using the Ares file-sharing program.

In addition, the Los Angeles County District Attorney’s Office charged Michael Becerra, 30, of Long Beach; Cristian Carrasco, 23, of Compton; and Andre Desire Loustau, 71, of Van Nuys, in Superior Court with possession of child pornography.