The explosion that injured four U.S. demining experts in Kompong Chhnang last week was caused by unfired ammunition, one of the people investigating the case said on Sunday.
Three U.S. Marines—Phillip McGill, Matthew Schaefer and David Crouse—and Len Austin, a contractor for Golden West Humanitarian Foundation, are in Bangkok recovering after the accident at the Cambodian Mine Action Center (CMAC) facility on Tuesday.
Roger Hess, director of field operations at Golden West, said he was in Kompong Chhnang on Sunday investigating what had happened.
Mr. Hess said he wished to clarify that the incident was caused by “unfired stockpiled munitions”—23-millimeter ammunition for an anti-aircraft machine gun—rather than unexploded ordnance (UXO).
“That caused a lot of disturbance in the [U.S.] Embassy and the military command because they were not supposed to be handling UXO,” he said.
The munitions were “totally safe to handle,” he said. “An accident occurred.”
CMAC director-general Heng Ratana said the organization was working together with Golden West and the U.S. Marine Corps to investigate the incident.
“Our investigation is in progress and we cannot yet make any conclusion,” he said.
Mr. Hess, who visited Mr. Austin at Bumrungrad International Hospital in Bangkok last week, said his colleague—who suffered injuries to his abdomen in the blast—hoped to return to Cambodia and continue his work this week.
“Len is recovering well,” he said, adding that he was now being kept in the hospital to monitor the risk of infection from his injures.
“I was not allowed to see the Marines…but I understand they’re recovering well,” he added.
