A four year-old girl in the United States has been rescued thanks to an internet child pornography investigation in Saskatchewan.

Saskatoon police Det. Darren Parisien said the case began with the arrest of a 21-year-old man in Marshall, Sask., near Lloydminster.

"The images were sent to this individual very, very recently — within days of us executing the search warrant — and the pictures themselves appeared to have been taken very recently," he said.

Parisien said the man was trading online pornography with a man in the U.S. and, using emails and text messages, police were able to track the girl and the man believed to be abusing her to Idaho.

Police passed the information along to U.S. authorities, Parisien said, and within 10 days of the Saskatchewan bust, a suspect had been arrested in the U.S. The victim he was abusing was identified and rescued.

"In this case, the child really was young enough that she hadn't disclosed or said anything and no one noticed anything, so no doubt that abuse would have carried on," he said.

"And even outside that abuse, someone who goes down that road once — there's no way that they're not going to go down it again."

Parisien said all the officers involved are grateful the little girl was rescued.

"When you're able to really identify a child and save a child, you kind of melt a little bit and you can't help but get caught up in the moment and obviously, that part of it becomes somewhat emotional," he said.

The Saskatchewan man's arrest could lead to the investigation of hundreds of other traders in child porn, Parisien said, which is why police have not released the man's name.