At midnight Sunday, 67 illegal aliens were arrested at the San Onofre checkpoint, Border Patrol Supervisor Mike Nicley said.
Agents became suspicious when a tractor-trailer rig parked for a long time at the weigh station so the passengers could use the restrooms, he said.
Agents searched the vehicle and found the aliens inside.
The driver, Hector Perez Fregoso, 29, was arrested without incident on suspicion of alien smuggling and booked into the Metropolitan Correctional Center, Nicley said.
Fregoso is a transient and legal U.S. resident.
Nine of the aliens were from Guatemala, two from Nicaragua, one from Colombia and 55 from Mexico, Nicley said.