The previously secret British Foreign Office documents show the prisoners were killed by guards at Hola prison camp, The Guardian reported Thursday. The documents show guards were allowed to treat prisoners who refused to work with great brutality and even lethal force.
Thousands of Kenyans died during the Mau Mau uprising in the 1950s, most of them Mau Mau fighters or suspected fighters. The colony became an independent country in 1963.
The Foreign Office files became known when Kenyans attempted to sue the government for mistreatment during the uprising. The files have now been transferred to the National Archives.
In one memo, Eric Griffith-Jones, the Kenyan attorney general, had a warning for Evelyn Baring, the colonial governor: "If we are going to sin, we must sin quietly."