WASHINGTON — Homeland Security investigators who uncover child exploitation initiated more than 4,000 cases around the world in the 2019 budget year, resulting in thousands of arrests and the identification of more than 1,000 victims, according to new data obtained by The Associated Press.

Their caseloads are growing because of the ease with which offenders can post graphic images of children online.

“With the dark web on there, the content is becoming more prevalent and more horrific,” said Matt Wright, the chief for the Child Exploitation Investigations Unit at Homeland Security Investigations.

HSI is a division of US Immigration and Customs Enforcement tasked with investigations, not immigration enforcement. Agents work on probes involving money, drug smuggling or child sex trafficking.

“While we are within ICE, our primary function is as criminal investigators,” said Joanna Ip, assistant director of the agency’s cyber division, which oversees the unit working on combating child exploitation. “We do criminal investigations with customs and immigration authorities — anything that comes in and out of the border.”

The numbers for the last budget year, which ran from Oct. 1, 2018, to Sept. 30, 2019, are higher overall than for the previous few years, according to the data, even as HSI’s parent, the Department of Homeland Security, remains focused on immigration enforcement.

Agents and investigators initiated 4,224 child exploitation cases that resulted in 3,771 arrests and identification of 1,066 victims.

The previous two budget years each saw about 4,000 investigations but lower arrests and fewer victims identified, according to the data.

On Thursday, officials plan to unveil a new center based at ICE’s Washington headquarters tasked with alerting other countries when US sex offenders are traveling there. The new center will include representatives from the US Marshals office and US Customs and Border Protection.

The idea stemmed from a pilot program in California in 2007. Investigators started using state sex offender registries and federal data to alert other countries when those registered traveled.

President Barack Obama signed a law in February 2016 mandating notification when registered sex offenders traveled. The notice doesn’t impede legal travel, but it does give countries a heads-up, especially in locations where child sex tourism and abuse are rampant, officials said.

Cheaper online storage and easier encryption tools are making for a vast increase in the number of exploitive images posted and traded online, HSI investigators said.

Wright said they’ve been able to implement new technology to help investigators sift through all the images and continually train agents and analysts.

“We’re trying to stay at the cutting edge of technology but also paying attention with what the offenders are using,” he said.

HSI agents number about 7,000 and some work at locations around the globe.