The incident occurred near Scarborough Shoal, one of two hotly disputed areas where confrontations between the two countries have flared since last year.
Minot Air Force Base, North Dakota, is in line for a nuclear-sized upgrade as the Department of Defense plans to update its nuclear deterrence capability.
On April 14, a National Guardsman assigned to Operation Lone Star "discharged a weapon in a border-related incident," the Texas Military Department said.