Disaster officials in Kisii battled a laboratory fire at Friends Secondary School, Giachere on Friday evening.
An official said they suspect an electric fault caused the inferno.
The fire broke out some minutes to 10pm, Dr Doris Nyokangi, the Kisii disaster manager said.
"My officers are already on the ground battling the flames," Ms Nyokangi said.
But Ms Nyokangi said further investigations will be held to establish the cause of the fire.