Four London-area residents have been arrested as part of a massive police investigation into online child exploitation.

Men from Chatham, St. Thomas, Woodstock, Stratford and Windsor are also facing charges.

The Ontario Provincial Police released details Thursday about the province-wide operation, which involved police agencies from around the province, as well as the Canada Border Services Agency and U.S. Department of Homeland Security.

In total, 80 people are facing charges after authorities executed 174 search warrants.

Police say they have identified 20 victims in the case.

As part of their investigation, the OPP identified more than 2,000 unique IP addresses across the province that were either “download candidates” for suspected child pornography, or showed that the user had visited a child exploitation website.

“These IP addresses were observed over the last 90 days in Ontario,” police said in the release.

Lianna McDonald, executive director of the Canadian Centre for Child Protection, said the arrests announced Thursday send a critical message to those who make, share and access child abuse material online.

“This is an important day for children in Canada,” she told the news conference.

McDonald said the national child protection centre receives an average of 4,000 reports of possible child abuse and online exploitation each month. Eighty per cent of child pornography images distributed on the internet involve children under the age of 12, and 80 per cent of the victims are girls, she said.