Authorities in Canada, the United States and the United Kingdom have arrested more than 150 individuals in connection with an international child porn investigation.

The 153 individuals were arrested as part of Project Mercury, a joint effort involving the Toronto Police Service, Ottawa Police, Saskatchewan RCMP, United States Homeland Security and U.K. National Crime Agency. The alleged offences date back as far as 2014.

Offenders allegedly sexually abused young children in live-streamed events that encouraged viewers to provide suggestions as to how the child was assaulted, according to the Toronto Police Service.

Toronto police Det.-Const. Janelle Blackadar says the investigation started in 2014, when U.K. authorities informed the TPS and other agencies of an online group allegedly involved in the sexual exploitation of children in several countries. Toronto police subsequently launched an undercover investigation, during which Blackadar says officers “observed the live abuse of a six-year-old child over the internet” in July of 2015. Blackadar says the alleged abuser was doing it for the sexual gratification of himself and for those online, “who actively encouraged the abuse while it was happening live.”

“Users commented amongst themselves, as well as directing the abuser,” Blackadar said.

“Unfortunately this was not the first time it happened, but I can tell you it was the last,” she said.

Blackadar said the pornographic material was being distributed around the world “using various social networking platforms.”

Toronto police also found “sexual abuse material involving an eight-year-old child” in 2015, according to a TPS news release. RCMP identified the individual in the video and rescued the child from an address in Saskatoon.

Police in other jurisdictions observed similar live-streamed events as the investigation widened, with two instances in December 2015 and October 2017 yielding 12 arrests and two children rescued.

A total of 13 Canadians have been convicted of child pornography-related charges in connection with the investigation. Another three cases are still before the courts.

Canadian jurisdictions involved in the case include Ottawa, Belleville, Ont., Thunder Bay, Ont., Edmonton, Saskatoon, Quebec, New Brunswick and Newfoundland.