WARNING: Some of the details in this story are disturbing.

Toronto police say the 2014 discovery of an online group allegedly involved in the sexual abuse of children has led to 153 arrests and numerous convictions in multiple countries and jurisdictions, including Canada.

The results of a three-year-investigation, dubbed Project Mercury, were announced by investigators from Canada, the U.K. and the U.S. at a news conference in Toronto Thursday.

Police said that after the National Crime Agency in the U.K. discovered the group in 2014, they reached out to various other police agencies as offenders and locations were identified.

The growing investigation led police to a number of disturbing discoveries.

As part of an undercover investigation in July 2015, officers from the Toronto Police Child Exploitation Section observed the sexual abuse of a six-year-old child being live streamed for the pleasure of the abuser, as well as for a participating online audience, police said Thursday.

“During the abuse of the six-year-old child, users commented amongst themselves, as well as directing the abuser,” Detective Constable Janelle Blackadar told reporters. “Unfortunately this was not the first time this happened, but I can tell you that it was the last.”

Blackadar said the abuser was identified in Pennsylvania within hours and the child was rescued.

Several people who allegedly watched and directed the abuse were subsequently identified by local police services and more than 20 alleged offenders were arrested.

In March 2016, an undercover Toronto police officer found child sex abuse material involving an eight-year-old child.

“The offender also was inviting members of this community to attend and engage in the sexual abuse of this child by drugging the child with narcotics to facilitate the abuse,” Blackadar said.

The child was identified as being in Saskatoon, Sask. Toronto police contacted local RCMP, who arrested a suspect within hours and rescued the child.

A Saskatoon man was subsequently convicted of multiple child porn-related charges and an application has been made to designate him as a dangerous offender, police said.

The investigation has led to the arrest and conviction of multiple alleged offenders, including seven in Toronto, two in Ottawa and one in each of Belleville, Thunder Bay, Edmonton, Saskatoon, Quebec, New Brunswick and Newfoundland.

“The success of this joint project with the National Crime Agency and Homeland Security Investigations, along with numerous other domestic and international partners is a great example of cooperation of law enforcement agencies with one common goal; to identify and safeguard children, no matter where they are in the world,” Blackadar said.

Graham Ellis of the U.K’s National Crime Agency told reporters that many of those arrested as part of the investigation were people who had occupied positions of trust.

“We’ve safeguarded 58 children as a direct result of this operation,” Ellis said. “We’ve also removed nine people from a position of trust. By that, I mean four teachers, a doctor, a member of police staff, an A&E nurse, a priest, and a private music tutor. We’ve also prevented a child being adopted by an offender and we’ve removed a child from foster care.”

He said the July 2015 incident observed by Toronto police led U.K. police to arrest and prosecute six offenders.

“Of those six, the most serious was a youth worker who drove vulnerable adults around the United Kingdom,” Ellis said. He was sentenced to 11 years in prison.

Other people prosecuted in connection with that incident included a charity worker and primary school teacher, Ellis added.

In all, Project Mercury involved 23 U.S. states, as well as the United Kingdom, Germany, Italy, France, Ireland, Denmark, Belgium and Slovenia.

Police have published a list of those charged and or convicted in Canada as part of the investigation.

Blackadar said technology has multiplied the potential for the sexual abuse of children and she said investigators are urging anyone with a sexual interest in children to come forward to police or health professionals to receive treatment rather than consuming child sex abuse material.