Marines are investigating after a 155mm artillery round exploded over Interstate 5, hitting California Highway Patrol vehicles with shrapnel.

Traffic delays could be significant Saturday with the U.S. military planning to fire live artillery rounds over Interstate 5 in Southern California. The freeway will be shut down temporarily Saturday afternoon.

During a live-fire demonstration at Camp Pendleton, a 155 mm shell prematurely detonated, causing shrapnel to hit a California Highway Patrol vehicle and motorcycle. Governor Newsom ordered the closure of a 17-mile stretch of Interstate 5,

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

CHP reports that a section of Interstate 5 in San Diego — from Harbor Drive to Basilone Road in Oceanside — will be closed from about 11 a.m. to 3 p.m

The military showcase has drawn has drawn strong objections from Gov. Newsom, who said safety concerns forced him to close a 17-mile portion of the interstate.

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 Marines are gearing up for their 250th birthday Saturday with a high-octane amphibious demonstration at Camp Pendleton's Red Beach, featuring amphibious vehicles storming the