Road users have been advised to exercise caution while using the superhighway.
Nairobi motorists have been handed reprieve by the governor.
He was among the 962,512 candidates who sat for the exam last year.
The incident comes amid a spate of abduction incidents across the country.
The MP revealed the details after a call with Education Cabinet Secretary Julius Ogamba.
The protests are likely to lead to heavy traffic congestion and disrupt business in the capital.
Videos and images obtained by Kenyans.co.ke showed hundreds of residents holding jerricans while rushing towards the scene.
The marathon will take place on Sunday, January 12.
This move by the Ministry comes amid focuses on the phase out of KCSE in the new CBC system.
The girl is among the candidates who sat for the recently released KCSE Exams.