More than a dozen international law enforcement organizations worked together under U.S. leadership to identify and locate victims of child sexual exploitation in a just-completed operation that officials say is likely the most successful of its kind.

In the three-week “surge” known as Operation Renewed Hope, which began July 17, investigators combing through sexually graphic internet material involving children, much of it on the dark web and some of it decades old, made probable identifications of 311 child victims and confirmed the rescue of several victims from active abuse.

Homeland Security Investigations, part of Immigration and Customs Enforcement, took the lead in the operation, which included representatives from the Justice Department, the FBI, the U.S. Marshals, Interpol and Europol, as well as 13 law enforcement agencies from Australia, Canada and countries in Europe and South America.

In many of the cases in which victims have been identified, HSI officials told NBC News, the material had existed for many years, but investigators were previously unable to identify the child victims or the adult abusers. Thanks to new facial recognition and artificial intelligence technology, there are now fresh leads in these formerly cold cases.

After they narrowed down a location or tentatively identified a victim, the investigators sent their new leads to the appropriate local law enforcement agency. The operation sent more than 100 leads to HSI field offices and 25 partnering countries. Some suspects in Canada and the United States have already been arrested.

The announcement comes a week after the FBI revealed it had identified dozens of victims of child sex trafficking and more than 100 suspects in a separate sweep called Operation Cross Country.

Mike Prado, deputy assistant director of the HSI Cyber Crimes Center, said the results of Operation Renewed Hope “exceeded our wildest expectations in the sense of being able to identify children who have been abused for, in many cases, years.”

He gave NBC News a tour of the operation while it was in progress, being careful to avoid showing any of the highly graphic material under review.

In one room, more than 20 investigators were gathered. Prado said they were “actively looking at some of the most egregious, some of the most depraved images that had been circulating on the internet for, in some cases, decades.”

Images enhanced via AI or machine learning, he said, can provide “our agents and investigators a starting point to begin an investigation or in some cases gives us a tentative identification where we’re sending leads out to the field to confirm the identity and rescue a child.”

The investigators used context clues such as the flora and fauna in the pictures, the species of birds singing on video, to geolocate the material and find the possible victims and perpetrators, Prado said. In one case, he said, investigators were able to identify a specific campground and then a victim and an abuser because of the type of fish the child victim was holding up in a photo.

When found, victims are treated sensitively, he said, and given resources to cope with their trauma, as well as the opportunity to testify in trials against their abusers. Some of the victims were as young as infants or toddlers when they were abused and are now being found as adults, he said, and in many cases, they have never been given counseling or services, and their abusers may still be preying on young children.

The investigators charged with reviewing the material in Operation Renewed Hope were given resiliency training, mental health resources, and an emotional support dog roamed through the rows of computers.

Despite the demoralizing nature of the work, Prado said, the investigators have reason for optimism because of the number of child victims they’ve been able to identify.

HSI handles more than 60% of the child sex abuse material cases in the U.S. with international reach. Before the dawn of the internet, this type of material was sent through the mail and the job of intercepting it fell to Customs agents, he said.

In fiscal year 2022, work by the Cyber Crimes Center and HSI field offices resulted in the identification or rescue of 1,170 child victims, and the arrest of 4,459 individuals for crimes involving the sexual exploitation of children.

Earlier this month, the FBI revealed that in Operation Cross Country, which was a two-week sweep, it had located 59 victims of child sex trafficking and child sexual exploitation and 59 missing children and identified 125 suspects.

On Tuesday, the Australian Federal Police said that as a result of Operation Bakis — a joint operation with the FBI — 19 men had been arrested on charges of sharing child abuse material online and at least 13 children were rescued from further harm. The latest cases brought the total number of people arrested as part of the joint probe up to 98, with at least 79 arrests so far carried out by the FBI, according to the Australian agency.