Eighteen Marines and one sailor from Camp Pendleton, Calif., are being held as military and federal law-enforcement officials probe their possible roles in a human smuggling operation. National Public Radio (NPR) reported that the Naval Criminal Investigative Service (NCIS) arrested 16 of the Marines, who were pulled out of formation. The suspects were not charged as of July 19. Two other Marines were arrested under related charges on July 3. The Marine Corps, U.S. Customs and Border Protection and NCIS have provided no further details, pending the outcome of their investigations. The NPR report stated that Border Patrol agents apprehended the two Marines as they were driving three Mexican citizens northward from the international border. The three passengers told authorities they intended to pay $8,000 to enter the U.S., NPR reported.