Egyptian border guards on Wednesday stopped 328 people from crossing to Libya through the southern gate of Salloum City and the Siwa oasis, Al-Ahram Arabic website reported.
They arrested five people from Sudan, and 323 from Cairo, Alexandria, Menya, Assiut, Beni Suef, Sohag, Beheira, and Fayoum.
The military prosecution is investigating the incident because the migrants were found in a restricted military zone.
Earlier this month, Egyptian border guards prevented 291 people, mostly Egyptians, from entering Libya.
Large numbers of people have been trying to flee Egypt to Europe via Libya. Many are migrants searching for a better life and hoping to find work.
The International Organisation for Migration estimates that between 330,000 and 1.5 million Egyptians worked in Libya until the ongoing unrest that began with the NATO-backed uprising that toppled Muammar Gaddafi in 2011.