The mishap, during an anniversary celebration for the Marine Corps attended by the vice president and defense secretary, underscores safety concerns that Gov. Gavin Newsom voiced before Saturday’s event at Camp Pendleton.

The decision to close Interstate 5 due to live-fire at Camp Pendleton was made early Saturday, a California Highway Patrol official told KPBS.

California closed part of Interstate 5 on Saturday after military officials confirmed artillery would be shot over the freeway. Then it reopened temporarily.

I-5 closes 11 a.m.–3 p.m. for Marine Corps 250th anniversary live-fire demo at Camp Pendleton; expect major SoCal traffic delays.

The artillery rounds were fired over Interstate 5 near Camp Pendleton in San Diego as part of a military demonstration for the Marine Corps' 250th anniversary.

The Monday morning crash created a miles-long traffic backup lasting nearly eight hours on Interstate 5 northbound in Portland.

UPDATE: Northbound Interstate 5 in Portland at milepost 299, near the split with Interstate 405, is back open after a two-truck crash. Traffic remains backed up and will take some time to clear, according to ODOT. Drivers were urged to slow down and watch for emergency responders still working in the area.

Northbound Interstate 5 is slowed going into Downtown Portland Monday morning after a two semi-truck crash, officials said.

An artillery round exploded over Interstate 5 at Camp Pendleton, cutting short the military's live-fire exercise.