Machakos Governor Wavinya Ndeti has urged security agencies to move swiftly and arrest suspects who set Machakos market on fire on Friday night.
The students are said to have smuggled the petrol into the school through a fence and hidden it outside a dormitory.
Five students from Magereza Academy have been charged with arson and malicious damage after allegedly setting fire to a school dormitory.
A Kakamega court has rejected a prosecution request to extend the detention of eight Mukumu Boys students over an alleged arson plot.
Nine Utumishi Girls students accused of arson that killed nine schoolmates appeared in court as prosecutors sought 30 days to complete investigations.
Kenyan police on Friday said eight students had been arrested over a suspected arson attack at a girls' school that killed 16 children and hospitalised 79 others.