A girl believed to have started a fire that killed her nine colleagues at Moi Girls in Nairobi will be arraigned this morning.
Police are likely to seek more time to detain the 14-year-old form one student in order to complete investigations into the matter.
Preliminary probe has shown that the fire started from her bed.
More than a dozen students grilled over the incident have mentioned her as the key suspect.
"The teenage student in question was earlier suspended from school over indiscipline, she was even walking with a matchbox in the school," one of the officers investigating the case said.
Preliminary police findings also show the young girl had threatened to "cause something horrific" after her parents declined to move her from the institution.
She allegedly tried to commit suicide after being suspended but she was later readmitted by the school management.
Arson is to blame for the Moi Girls' fire that claimed nine lives, Education CS Fred Matiang'i said on Monday.
Matiang'i, who doubles as the acting Interior CS, said this was the conclusion after thorough investigations by police.
"It was not an accident, it was arson," he said following the incident during which seven pupils were killed.
He said two out of 10 injured students later succumbed to their injuries.