Kaing Guek Eav, also known as Duch, was unable or unwilling to identify many of the people in photos given to the Documentation Center of Cambodia, The Phnom Penh Post reported.
Duch is serving a life sentence for crimes committed while he was chairman of the Phnom Penh detention and interrogation center known as S-21, where the unknown Westerners and many others were tortured and died.
Savina Sirik and Kok-Thay Eng of the documentation center interviewed Duch for 2 hours Wednesday. He told Sirik he was unable to remember the names of any of the people in the photos he was shown.
Sirik said Duch told her only four Westerners were imprisoned at S-21 "and he didn't really remember the faces of those people."
Photos of the two Western-looking men were among 1,427 images anonymously donated to the documentation center earlier this month
Most of the photos in the collection are of people from Thailand and Vietnam.
One of the two photos may be of Christopher Edward DeLance, who was seized in 1978 while sailing off the coast of Cambodia, the newspaper said.
Three other Americans also died in S-21 -- Michael Deeds, James Clark and Lance McNamara.
All four men were tortured into confessing they worked for the Central Intelligence Agency, the Post said.