Two children who were rescued as part of a provincewide child pornography investigation that resulted in 31 arrests are just the tip of the iceberg, and there are likely thousands of other kids out there still being exploited, an Ontario Provincial Police officer said Thursday.

"Unfortunately I believe there's thousands of children we're not getting to, and that's particularly difficult," said Insp. Andrew Stewart, who manages the police force's child sexual exploitation section.

"When we do rescue children, of course it is tremendously satisfying, and that's what we're here for. We're here to protect children."

Police didn't say much about the rescued children — only that they are a 12-year-old girl and four-year-old boy who are now in care and receiving the appropriate treatment.

Their rescue was detailed Thursday during a news conference where police announced that the largest co-ordinated child pornography investigation of its kind in Ontario had led to a total of 93 charges laid against 31 people. Three of the accused are youths, while the oldest is a 60-year-old man.

The arrests are a direct result of, among other things, improved tools to track down alleged child pornographers on the internet, said provincial police Commissioner Julian Fantino.

"The internet continues to pose a threat to children, parents, and certainly we feel challenged in our ability to keep up, to keep pace, with the pervasive use being made of it by those who seek to victimize children," Fantino said.

'Determined effort'

"The arrests ... are directly attributed to the acquisition of better equipment, consistent training, centralized co-ordination and a determined effort to do all we can to protect our children."

The charges include sexual assault, sexual interference, making child pornography, distribution of child pornography, and possession of child pornography.

More charges are pending, police said.

Fantino said the reality for police is that they are in "catch-up mode" when it comes to arresting perpetrators. He said while he and his colleagues must follow the parameters of the law, those making and distributing child pornography are constantly trying to stay a step ahead of police. He said one solution would be for the federal government to act to improve the national sex offender registry.

"One of the things we need badly is a national, effective, efficient [sex offender] registry that would enable us to be even more vigilant," he said.

Fantino said the National Association of Police Chiefs has been asking for improvements to the national registry for some time, but nothing meaningful has happened.

"We just keep on asking, and we hope that with examples such as this ... a true portrayal of our needs are then reflected."