Eight candidates were found with mobile phones in examination rooms, Education CS George Magoha has said.
Addressing the media on Thursday, Magoha said 15 cellphones were also confiscated.
"The phones were confiscated from various centres and are with the authorities as investigations continue. We want to find out what are in the phones," he said.
Magoha further warned parents against buying fake papers that are circulating in the market.
"There are people selling fake papers. Parents, do not be duped to buy these papers. There is no exam that has leaked," he said.
But he noted that the examination process went on well adding that all elaborate guidelines have been followed.
Early exposure of KCSE exam papers to candidates is the new headache facing the Education ministry in its efforts to curb cheating.
Explaining the 'early exposure' concept, Magoha said some officials open the papers minutes before the exam start time, give the questions to teachers who in turn share them with the candidates.
“Unprofessional examination officials expose the exams a little earlier than the scheduled time. The questions are then shared to the targeted candidates just before the examinations start,” Magoha said.
The Kenya National Examination Council termed the start of the tests last Friday a success. It will end on April 21.
Students will take a maximum of two papers a day as has been the case since 2016.
Some 752,933 candidates are sitting the exam in 10,437 centres.
It is the 32nd examination in the history of the Kenya Certificate of Secondary Education and comes amid the Covid-19 crisis.
On Monday, Magoha said Kisii county, Homa Bay and parts of Isebania, were cheating hotspots that were being closely monitored.
