Hundreds of people from around the world have reached out to the FBI since agents asked for help in their investigation of a teacher accused of drugging and molesting boys over his decades-long career, mostly outside the U.S.
William Vahey committed suicide in Luverne, Minnesota, on March 21, just two days after federal agents had applied for a warrant to search his USB thumb drive.
At the time of his suicide, he was a teacher in Nicaragua. When the school's director confronted him about the photos on his USB drive and demanded his resignation, he traveled to the southwestern Minnesota town, where he had family, and killed himself in a hotel room, the Associated Press reported.
It has not been reported whether any of Vahey's victims were from Minnesota. The FBI has a list of places where he taught, mostly outside the U.S.
The FBI has called Vahey "one of the most prolific pedophiles in memory," the AP reports. The FBI said the USB drive contained at least 90 pornographic images of boys, ages 12-14, who appeared to be asleep or unconscious.
But now, the FBI believes the number of victims could be much higher.
Last month, federal agents announced they wanted potential victims to contact them so they could get counseling and perhaps provide more information about the investigation.
Special Agent Shauna Dunlap told BBC News Tuesday the FBI has "been contacted by several hundred individuals from around the globe wishing either to reach out as potential victims or provide information in the ongoing investigation."
The FBI says Vahey drugged the boys with sleeping pills and was able to molest and pose them for nude photos, without the victims even knowing what happened to them. The AP says Vahey would hand out sleeping-pill laced Oreos at bedtime while they were on school trips.
Vahey had a history of sex offenses and clues into his actions may have gone unnoticed, according to reports.
The FBI says Vahey pleaded guilty to one count of child molestation in California in 1969 and the terms of his conviction required him to register with California's sex offender registry for the rest of his life. But he hadn't renewed his registration since 1970.
The BBC notes that the lapse in registration allowed Vahey to work at 10 schools in nine countries from 1972 to 2014.
While he was teaching in Venezuela, between 2002 and 2009, two students under Vahey's watch were rushed to the hospital because they were unconscious in their hotel room on a trip, the AP reports. Officials weren't able to figure out why and blamed it on a possible faulty air conditioner, AP says.
Sir Chris Woodhead, the head of Southbank International School in London, told Britain's Press Association there was one complaint about Vahey while he worked at the school from 2009-2013, but the boy's parents agreed that it shouldn't be pursued.
Images of 50-60 students at the Southbank school were found on Vahey's thumb drive, the BBC says.
Woodhead told the Belfast Telegraph he believes "devious and sophisticated" offenders could "slip through the net" even when there are policies in place. He added that schools must make sure nothing like this can happen again.
Since the allegations against Vahey surfaced, international schools have started to review recruiting policies, background checks and security procedures. The Council of International Schools announced Tuesday it has launched an International Task Force on Child Protection to look at its current practices.