(OTTAWA) - Nine Canadians have been charged in an ongoing global child sex abuse investigation prompted by the discovery of a 2006 video depicting sisters being raped by their father, police said Tuesday.

Almost 100 Canadians who corresponded by email with the videographer, an Italian national arrested last year, are also being investigated, said police.

"The evidence indicates that those in possession of this material did not find it accidentally," said Superintendent Earla Kim McColl, of the Royal Canadian Mounted Police.

"They sought it out, they previewed the samples, they paid in advance and they waited for a password to download the videos."

The probe, labeled Operation Koala, started in Australia where authorities in 2006 discovered a video of the rape of two girls, who were 9 and 11 years old, performing oral sex on each other and being raped by their father.

The video was traced to Belgium and the man in the video was arrested.

Thereafter, the investigation led to an Italian videographer with a private studio in Ukraine, where he produced 150 videos.

Menno Hegemeijer of Europol told reporters the videographer had "documented the sexual exploitation of underage girls, some barely school age," and sold the videos online.

"This offender also provided the opportunity for others to special order videos to their specifications. Some traveled to the studio to watch the abuse recorded live or participate in it for an additional fee," he said.

After going through 50,000 emails between the videographer and his customers worldwide, Europol identified some 2,500 buyers of his pornography, including 100 in Canada.

Twenty-one Ukrainian victims, aged 9 to 16, were also identified.

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