Story highlights Some of those charged shared offending videos hundreds of times

Police were tipped off to the illegal activity by Facebook

(CNN) More than 1,000 young people in Denmark have been charged with "distribution of child pornography" after sexual content featuring 15-year-olds was circulated online, Danish National Police said in a statement Monday.

The police launched an investigation following a tip-off from Facebook about two videos and a "sexually explicit" image that were being circulated by mostly teenage social media users across Denmark.

"It's a very big and complex matter that has taken a long time to investigate. Not least because of the large number of those charged," North Sealand police inspector Lau Thygesen said in a statement.

"We have taken the case very seriously as it has major implications for those involved when such material is spread."

The majority of those charged shared the video a couple of times, but some did so hundreds of times, police said.

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