The FBI is seeking more information about Child predator William James Vahey.
Vahey committed suicide last month, two days after US agents filed for a warrant to search his computer thumb drive.
The US Federal Bureau of Investigation (FBI) said the device contained pornographic images of at least 90 boys, aged 12 to 14, who appeared to be drugged and unconscious.
The FBI said the photos dated from 2008 or after, but that Vahey may have abused children for decades and are looking for more information.
Vahey was jailed for child molestation in California in 1969 but went on to work at international schools around the world over four decades.
A British private school has confirmed that images of more than 50 of its students were found on Vahey’s computer.
Southbank International School’s chair of governors said Vahey went thorough a criminal records check before starting work in London.
“You would have thought that within America itself, the fact that he had a conviction for child abuse would have prevented him from becoming an accredited teacher in the United States,” said Sir Chris Woodhead.
“It is a complete mystery as to how he taught from, I think, 1972 onwards in international schools throughout the world with this conviction behind him,” added the chair of governors.
British police said they had searched a London property in connection with the case and were working to identify and support potential victims.