A huge explosion in southwestern Cambodia over the weekend that killed 20 soldiers at an army base appears to have been an accident caused by mishandling of ammunition by troops, a senior military official said Tuesday.

The Saturday afternoon blast in Kampong Speu province also destroyed military vehicles and four buildings at the base, and damaged homes in a nearby village.

Army spokesperson Maj. Gen. Mao Phalla said the soldiers were transferring ammunition from trucks into a storage facility when the blast occurred, killing them instantly. He said another 11 people, including soldiers and nearby villagers, were slightly injured, mostly from debris from the damaged buildings, not shrapnel.

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Cambodia held a mass funeral on Sunday for those killed in the explosion.

Cambodian soldiers' relatives gather for the funeral procession to all who died during an ammunition explosion in an army base in Kampong Speu province, Cambodia

Cambodian soldiers' relatives gather for the funeral procession for all who died during an ammunition explosion in an army base in Kampong Speu province, Cambodia, on April 28, 2024. (AKP via AP, File)

The initial but still not official theory was that the soldiers were unloading ammunition from a truck and stacking it on the ground before moving it into the storage facility, causing one item to explode, he said. That set off a chain reaction, added Mao Phalla.

However, he said it will be difficult to determine the exact chain of events as all those involved in the unloading were killed.

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Mao Phalla said the site has been sealed off and that deminers from the Cambodian Mines Action Center were clearing the area any unexploded ordnance.

In March 2005, a nighttime blast at an arms depot in the northwestern provincial town of Battambang triggered an hourslong spray of shells and bullets that killed at least six people and caused panic.

A 2014 report by the Swiss-based group Small Arms Survey highlighted the dangers of poorly stored or mishandled munitions, calling it a "global problem." It noted that from 1979 through 2013 there were more than 500 incidents involving unplanned explosions at munitions sites.