Nobel laureate Egyptian-American chemist Ahmed Zewail died Tuesday of an unknown cause.

"The cause of death is unknown ... whether it is cancer or something else ... His doctor said his condition was stable the last time I called him last week," Zewail's spokesperson Sherif Foad said, according to Reuters .

Zewail was awarded the Nobel Prize in Chemistry in 1999 for his work in femtochemistry, the study of chemical reactions that happen in short timescales.

At that time, Zewail was the third Egyptian national to receive a Nobel Prize, following Anwar Al-Sadat in 1978 and Naguib Mahfouz in 1988. He was also the first Arab to win a science Nobel, with most Arab laureates having won the Peace Prize.

Born in Damanhur, 160 km northwest of Cairo, Zewail studied at Alexandria University. He later moved to the United States to complete his doctorate at the University of Pennsylvania.

In 1976, Zewail became a member of the California Institute of Technology (Caltech) and a professor of chemistry and physics at the University of California at Berkeley.

Zewail was a science and technology participant in U.S. President Barack Obama's Presidential Council of Advisors on Science and Technology, a group composed of leading scientists and engineers helping with policies in relevant fields.

He was also among the first U.S. science envoys to the Middle East in 2010, alongside Elias Zerhouni and Bruce Alberts.

Throughout his lifetime, Zewail published 600 scientific articles and 16 books, a legacy that will remain with us in his absence.