The bomb threat comes as the US selects a new ambassador to Cairo.
Security forces near Simon Bolivar Sq., Garden City, have detained a man after he threw an explosive device near the US Embassy, Reuters reported.
The man was stopped near the concrete barriers surrounding the embassy.
The US Embassy has issued an official notification, telling US citizens to monitor local media and stay clear of its surroundings.
This comes as the US selects resumes its ties with Egypt after a year of having no ambassador and frozen military aid. Asharq Al Awsat has reported US veteran diplomat David Satterfield would be the most likely candidate for the post.
More news on the bomb threat to follow.