SAN DIEGO (AP) — An investigation into Marines accused of helping smuggle migrants into the United States led to the arrest Thursday of 16 of their fellow Marines at California's Camp Pendleton, just north of the U.S.-Mexico border.

In a dramatic move aimed at sending a message, authorities made the arrests as the Marines gathered in formation with their battalion.

None of the 16 Marines were involved in helping enforce border security, the Marine Corps said in a news release. They are accused of crimes ranging from migrant smuggling to drug-related offenses.

Officials could not immediately be...