The U.S. military has deployed “sniffer aircraft,” drones and U-2 spy planes in preparation for a possible North Korean nuclear test, NBC News reported.
The sniffer aircraft is capable of detecting evidence of a nuclear explosion, according to NBC News.
In a statement to NBC, the U.S. Air Force said the plane, known as the WC 135, "has been deployed on a routine mission to Northeast Asia. These missions are planned well in advance."
Officials also told NBC that a nuclear test by North Korea could come without warning.
"We expect that they are able to do it at any time, without any real warning," one official said. "They have been engaging in steady preparations."