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Five children in four provinces have been rescued after a national investigation that targeted alleged child sex offenders, the RCMP said Thursday.

More than 150 people have been arrested or are under investigation as part of the operation that began in February, and more than a million images have been seized, some involving infants, the Mounties said.

"I cannot stress enough what these images are and what they are not," RCMP Sgt. Michael Petrilli told a news conference in Halifax.

"These images are not simply children having a bubble bath. They are clearly children that are in a situation where they are being sexually assaulted."

Investigators say two of the children who have been rescued are from British Columbia, and the other three are from Ontario, Quebec and New Brunswick.

More than 40 police agencies were involved in the investigation.