Maranda High School has been closed indefinitely following a fire that razed a dormitory at dawn Thursday.
Police are holding two men found within the school compound. The men were wearing the school's prefect uniforms but were not students.
One of them was roughed up by the pupils, before being handed over to the police.
County Director of Education Nereah Olick said that a meeting with teachers and stakeholders decided to close the school indefinitely because security had been compromised.
Nothing was salvaged from the fire, which destroyed the belongings of 140 students.
Thursday's dorm fire was the second such incident after another one was set on fire Monday night.
The school deputy principal Bob Otieno said that the incidents were acts of sabotage.
The neighbouring Nyamira Girls School was also closed down as a precaution.