A family source said Mr Muhammed, 23, was picked up by officers on November 8 on the campus ground of Federal University Dutse, Jigawa, and subsequently transferred to Abuja.
Mr Buhari described the deceased as “a natural versatile teacher,” fully integrated as a member of his family.
He asked that “well-equipped ambulances for the operation of NYSC mobile clinics” be donated to the scheme.
This indefinite leave comes a day after new photos of Mrs Buhari looking heavily pregnant went viral on social media.
The summit is targeted at state first ladies and gender-focused institutions, with Bisi Fayemi as the Keynote speaker and Besty Obaseki, as the session chair.
The first lady has been out of public glare for long, abandoning her duties as the president’s wife.
