Emergency rescue teams were searching the dormitory at Utumishi Girls Academy, where the fire started at about 1 a.m. (2200 GMT), radio station Capital FM said, citing Samuel Ndanyi, the regional police commander, Reuters reported.
"It is a distressing and saddening situation," county police official Masoud Mwinyi told distraught parents outside the school, said another broadcaster, Citizen Television.
Firefighters and police officers had fanned out to control the blaze and evacuate other students, Capital FM added. The cause of the fire is not yet known.
In 2024, a fire killed 21 students at a primary boarding school in nearby Nyeri County.