Marines attach a Joint Light Tactical Vehicle to a CH-53E Super Stallion helicopter during a jungle-warfare exercise in Kin Blue, Okinawa, on Feb. 16, 2023. (Alpha Hernandez/U.S. Marine Corps)

CAMP FOSTER, Okinawa — U.S. Naval Hospital Okinawa, prepped for a mass casualty exercise on Thursday, suddenly found itself handling the real thing.

A Light Tactical Vehicle with eight to 10 Marines aboard rolled onto its side at the Jungle Warfare Training Center on the island’s north end, 3rd Marine Division spokesman Maj. Clay Groover told Stars and Stripes by phone Thursday afternoon.

Some Marines suffered potential concussions, back pain, soreness and dizziness, but none of the injuries were life-threatening, Groover said.

“There will be an investigation on this afterwards,” he said. “Everyone seems to be OK at this point.”

At 1 p.m. the naval hospital, where the Marines were being treated, alerted its Facebook followers it was involved in a “real world” mass casualty event.

“USNHO is currently experiencing a real world mass casualty event,” the post said. “Please avoid the Emergency Department for non-emergent needs.”

The hospital posted the message under the heading “Real World Actual.”

The message led to confusion among about a dozen commenters, who said the message must be a mistake because the hospital a day earlier had posted that it would hold a mass casualty exercise Thursday.

Other commenters on the post, some claiming to work for the hospital, said an actual incident had occurred, overlapping with the drill.

After an hour, the hospital around 2:10 p.m. replied: “This is not an exercise. We are currently experiencing a real-world emergency involving multiple patients.”

It provided no other immediate details.

Stars and Stripes reporter Mari Higa contributed to this report.