Shrapnel from artillery that was detonated during celebrations for the US Marine Corps hit at least two vehicles on a California highway on Saturday, officials have said.
The event, celebrating the Marines' 250th birthday, was attended by Vice President JD Vance, and included live munitions being fired. The California Highway Patrol said one detonated overhead prematurely and struck two vehicles that were part of Vance's protective detail.
It came as state officials and the White House fought over a decision to close part of Interstate 5 for the event in southern California.
Firing live rounds over a busy highway isn't just wrong - it's dangerous, Governor Gavin Newsom, a Democrat, said.
The highway patrol said no injuries were reported and they notified the Marine Corps, which then cancelled firing any further munitions.
This was an unusual and concerning situation, Border Division Chief Tony Coronado said in a statement, adding that such exercises are not common over an active freeway.
Newsom said he closed a section of the Interstate 5 due to extreme life safety risk and distraction to drivers, including sudden unexpected and loud explosions.
Before they were aware of the mishap, officials in the vice-president's office had disputed that the demonstration was dangerous, and accused the California governor of trying to stoke fears.
The BBC has contacted the White House and vice-president's office about the shrapnel incident.
If Gavin Newsom wants to oppose the training exercises that ensure our Armed Forces are the deadliest and most lethal fighting force in the world, then he can go right ahead, William Martin, Vance's communications director, told CNN, before reports about the incident were known.
The First Marine Expeditionary Force at Camp Pendleton said in a statement that it was aware of the incident concerning a 55-millimeter shell fired during the event, and that an investigation was underway.
The demonstration was the largest in a decade in the continental US, the Marines said, and involved fighter jets, Navy vessels, helicopters and live fire from a towed howitzer.
During his remarks in front of hundreds of marines, Vance recalled his time in the force, railed against the government shutdown and critiqued previous military diversity initiatives.
