The fire at the Utumishi Girls Academy started in the early hours of Thursday while the students were asleep.
Police said search-and-rescue operations were under way with authorities yet to establish the cause of the fire. The Kenya Red Cross said emergency responders were on ground to offer support.
The education minister said the fire broke out on the first floor of one of the dormitories, which was "completely destroyed" in the blaze.
"The response teams managed to put out the fire by about 03:00, but by then the damage had already been done," he said.
