Firefighters from the Nairobi City County put out the fire that started at around 9pm.
A teacher from the school who spoke to the Star on phone said that no casualties were reported.
"All the girls are fine. We are doing a head count to confirm that all students are safe," Domitillah Ngoko said.
Public relations officer at the National Disaster Management Unit, Pius Maasai, said that no casualties were reported.
"It is unfortunate that fire incident has been reported at St. George's Girls High School, kitchen. So far no injuries have been reported and the cause of fire still remains unknown," Maasai said in a statement.
This incident comes a week after another fire killed nine students from Moi Girls Nairobi.
Courtesy Rhoda Adhiambo