SAN YSIDRO, Calif. -- U.S. Customs and Border Protection officers arrested a U.S. man Tuesday morning after they say he tried to smuggle three migrants into the country hidden in the seats of his vehicle.

CBP officers said they encountered the driver, a 33-year-old resident of Rosarito, Mexico, as he entered the port at about 5 a.m. driving a GMC Vendura van.

SLIDESHOW: Images From Arrest

According to authorities, the driver stated he was a citizen of the United States and presented a valid California identification and birth certificate to the officer.

The primary officer said the driver has a nervous demeanor. The officer referred the vehicle and occupant to a secondary lot for a more in-depth examination.

In the secondary lot, CBP officers discovered three undocumented migrants sewn into three seats of the conversion van, including the driver’s seat. CBP officers said they carefully extracted two men and a woman from inside the seats.

Officers determined that the two men and woman are citizens of Mexico. They are being detained as material witnesses in the prosecution case.

The driver was charged with alien smuggling and was transported to the Metropolitan Correctional Center to await arraignment. The vehicle was seized by CBP.

"This case illustrates the length to which smugglers will go to transport undocumented people into the United States," said Adele Fasano, director of field operations in San Diego. "This involved good basic police work by alert CBP officers who intercepted this case."