SAN DIEGO -- Border Patrol officials said Monday that they arrested more than 60 illegal immigrants over the weekend during a traffic stop.

Authorities said they stopped the semi truck in East County at a checkpoint near the Kitchen Creek Road exit on Interstate 8 on Saturday at about 9:15 p.m. Border Patrol officials said they interviewed the driver, who admitted being an illegal immigrant.

Border Patrol agents brought in a K-9 to search the truck, and officials said they found 61 illegal immigrants hiding behind bales of cardboard. Investigators said they believe the immigrants entered the trailer through a trap door in the floor of the trailer.

Officials said they seized the big rig and will prosecute its 29-year-old driver, identified as Jose Pina Flores, for immigrant smuggling.