A joint state-federal investigation was under way to see if there was any terrorism connection but no link had been found yet, FBI spokeswoman Denise Taiste said. The Navy base is the site of a brig where enemy combatants have been held.
Ahmed Abda Sherf Mohamed, 24, and Yousef Samir Megahed, 21, both students at the University of South Florida in Tampa, were being held Monday pending a bail hearing, Berkeley County Sheriff Wayne DeWitt said.
"They admitted to having what they said were fireworks. Based on the officer's judgment at hand, based on what he had seen, we judged it to be other than fireworks," DeWitt said.
The sheriff refused to say what was found in the car, but said some items were being analyzed by the FBI. Taiste would not give any details on what was in the vehicle.
Mohamed is a native of Kuwait and Megahed is Egyptian, the sheriff said. Both are in the country legally but it's not clear if they are U.S. citizens, DeWitt said.
The two men were stopped for speeding Saturday night near Goose Creek on U.S. Highway 176.
Goose Creek is the site of the Naval Weapons Station, which houses the U.S. Naval Consolidated Brig, a military prison where enemy combatants have been held. They were heading west, away from Goose Creek, when they were pulled over about seven miles from the sprawling Navy facility, police said.
Officers became suspicious because the men quickly put away a laptop computer and couldn't immediately say what they were doing in the area or where they were going, DeWitt said.
One item found in the car was destroyed by bomb technicians, making a loud bang when it was detonated.
Authorities closed a mile-long stretch of the highway Saturday night and didn't reopen it until about 4 a.m. Sunday.
Goose Creek, with a population of about 30,000, is about 20 miles north of Charleston.