Tech Sgt. Chuck Marsh says the explosion happened in southern Afghanistan. Officials released no other details, including what branch the troops served in or where the blast occurred.
Southern Helmand province is the site of the largest U.S. Marine operation since the 2001 invasion to oust the Taliban regime. Some 4,000 Marines are taking part. They have met little resistance from Taliban fighters but have had to contend with dozens of roadside bombs hidden in the region's dirt roads.
July has been the deadliest month for U.S. forces in the almost eight-year war. Thirty-four have now died. The U.S. has close to 60,000 troops in Afghanistan, a record number.