A fierce fire destroyed dormitory at the Senior Chief Koinange Girls high school in Kiambu county on Tuesday.
Villagers joined in efforts to contain the fire suspected to have been started by some students.
Police, however, say there were no injuries reported since the fire broke out at 5am.
Police and other witnesses say students' valuables have been destroyed in the incident.
Fire engines from the Kiambu county government joined in the efforts to contain the inferno.
Investigations to establish those behind the arson is ongoing amid claims some of the students had demanded to be sent home over undisclosed reasons.
Two dormitories were on Sunday burnt down at Kenyatta Girls' high school in Nakuru county.
Schools reopened for the third term on August 27.
Before closure of second term, there was a series of school fires countrywide in what security bosses attributed to rising cases of student indiscipline.