Two pilots were killed when their U.S. Army Apache helicopter crashed in South Korea on Monday, officials said.
The AH-64 Apache came down 50 miles east of Camp Humphreys, an American military base in the city of Pyeongtaek, the U.S. Army in South Korea said in an emailed statement to NBC News.
The cause of the crash near Wonju was not immediately clear. The identities of the pilots, who were the only people aboard, were being withheld until their families were informed.
According to South Korean news agency Yonhap, authorities there believe the chopper may have hit high voltage power lines or a "steel tower," perhaps referring to an electricity pylon. A power line was tangled up among the wreckage and the top part of the tower was damaged, the news agency reported.
"We offer our heartfelt prayers and condolences to the families of the soldiers involved in this tragic incident," said Lt. Col. Mark Gillespie, the deputy commander of 2nd Combat Aviation Brigade. "Our first priority is to provide their families with the support they need during this difficult time."
About 28,500 U.S. troops are stationed in South Korea, according to Reuters.
Meanwhile on Monday, South Korea's military conducted artillery live-fire drills on islands near a disputed maritime border with North Korea, ignoring Pyongyang's threat to fire back if any of the shells landed in its waters.