Five men involved with a Toronto-area web hosting company have been arrested on allegations that they knowingly allowed their servers to be used by a child porn website with tens of thousands of users.

Ontario Provincial Police announced the arrests Thursday, saying the men were involved in operating YesUp Media. They allege that one of YesUp’s clients was a man who wanted to use its servers to host a website for the uploading and downloading of pornographic images of children.

Tips regarding the website’s existence started coming to police attention in 2012, Det.-Insp. Dave MacDonald told a press conference on Thursday.

“People from around the world were seeing, basically, advertising for this website and were discovering really intense child porn,” he said.

“These are not simple images of children in bathing suits. These are really, really horrific.”

McDonald said police initially searched YesUp’s servers believing they were dealing with approximately 800 child porn files. They soon discovered that the number was much larger, and represented one petabyte (1,000 terabytes) of data -- more than the OPP had the capacity to store at the time.

According to police, the website hosted by YesUp had 60,000 registered users from at least 116 countries, nearly 20,000 of whom paid for “premium” subscriptions which allowed them faster download speeds and other perks. Files from the site had allegedly been downloaded more than 19 million times.

Police believe this is the first time in Canada that charges have been laid against people affiliated with a web hosting company in relation to the content of one of their clients.

“This investigation should serve as a wake-up call for those who victimize our children,” OPP Commissioner Thomas Carrique said at the press conference.

“Not only are police taking out the customers who abuse children online, we’re taking down the infrastructure that holds their monstrous content.”

All five men were arrested last week. They were identified Thursday as 52-year-old Chin Choi (Peter) Kok of Richmond Hill, Ont., 31-year-old Wen (Larry) Li of Toronto, 47-year-old Sui Hua (Jeff) Ye of Aurora, Ont., 40-year-old Zhen He (Patrick) Zeng of Richmond Hill and 42-year-old Zhen Yu (Jeff) Zeng of Richmond Hill.

They face charges ranging from making child porn available to access child porn to failure to report child pornography. Canadian law mandates that internet service providers must report all instances of child pornography they discover.

“We believe they were aware that child pornography was being hosted on the website,” MacDonald said.

A Canada-wide warrant has also been issued for a sixth man, whose identity has not been released publicly and who is believed to be in Vietnam.