A federal grand jury has added more charges against two Egyptian college students accused of illegally carrying explosive materials.

A grand jury issued a new indictment Wednesday charging former University of South Florida students Ahmed Abdellatif Sherif Mohamed and Youssef Samir Megahed with an additional charge of possessing a destructive device, the U.S. Attorney's Office in Tampa said.

Deputies in South Carolina who stopped their car last August said they found items to build pipe bombs in the trunk.

Mohamed also faces new charges of providing material support to terrorists and possessing a pistol and a rifle in violation of visa guidelines.

The FBI said he made a video demonstrating how to convert a remote-control toy into a detonator for a bomb.