The instructors were reportedly preparing a device for use as a teaching aid Tuesday when it exploded at a training site in Kampong Chhnang province in central Cambodia, the Phnom Penh Post said.
"The four injured US personnel were assisting in training for humanitarian mine action explosives ordnance disposal when the incident occurred," US embassy spokesman John Simmons confirmed.
Doctors in Phnom Penh said one victim was being operated on after suffering internal bleeding and an injury to a leg artery, the Post said.//DPA