An international child pornography ring was officially closed Thursday with convictions in a Missoula federal courtroom.

U.S. Attorney for Montana, Michael Cotter, said the case actually began in 2012 and stretched over two continents with law enforcement agencies in Montana, the FBI and agencies in Great Britain all taking part in the investigations.

"It was a very complex investigation that began with a report in 2011 of child pornography," Cotter said. "The FBI, Homeland Security and the Internet Crimes Against Children Task Force carried out a search warrant in Polson, Montana at the residence of 49 year-old Paul Wencewicz. They learned hat he was operating an online bulletin board where members would trade explicit images of little girls, some as young as 4 years old. That led to another bulletin board that was housed in a server on the Isle of Jersey, one of the Channel Islands of the United Kingdom. They were able to crack the encryption and retrieve a complete copy of the first bulletin board to help identify other criminals who were participating in the board."

Cotter said the trials were held in federal court, and the sentences handed down are not eligible for parole.

"We obtained 21 convictions, and the men ranged from 25 to 67 years of age," he said. "The sentences imposed by Judges Molloy and Christensen ranged from 180 months to 220 months. The men are now in prison for a significant period of time, and will be monitored for life following their release."

Cotter said these defendants were extremely dangerous.

"They were exploiting children as young as four years of age, and some had images of girls that were even younger, and some had as many as six million images in their collections," he said.

Cotter praised the cooperation of law enforcement agencies around the world to bring these individuals to justice.

"It's cooperation between international agencies," he said. "The work that is done locally by our federal agents, the Assistant U.S. Attorney in partnership with the state and also law enforcement in the United Kingdom. It is truly where men and women park their egos and their badges at the door and they are working with one goal in mind and that is to disrupt these organizations and bring meritorious prosecutions into the U.S. Attorney's office."

Cotter said as satisfying as it was to close this case, he knows that law enforcement is just scratching the surface of the worldwide plague of child pornography.