North Korean Test Not Likely a Hydrogen Bomb, US Officials Say

State media said country had successfully used an H-bomb.

— -- Initial test results suggest that an explosion in North Korean was not a hydrogen bomb, as the state government there has claimed, U.S. officials told ABC News.

That would be in the range of previous North Korean nuclear tests, including the latest one in 2013, and not a hydrogen bomb, which would have resulted in much higher energy output. The state-run news agency announced the "successful" tests today.

White House spokesman Josh Earnest echoed these sentiments in a news conference this afternoon, saying that initial data is “not consistent with North Korean claims of a successful hydrogen bomb test.”

Another official said a conclusive determination will be made after airborne samples are gathered but, for now, based on the size of the yield and scope of the blast, the initial reading is North Korea did not test a hydrogen bomb.

A U.S. Air Force WC-135 "Constant Phoenix" sniffer plane will soon be operational near North Korea, looking for radioactive isotopes that will help determine what kind of blast occurred.

The aircraft is used to monitor nuclear test ban agreements but is also used by the United States after North Korean nuclear tests to look for isotopes that may have escaped into the atmosphere. The plane has equipment that gathers samples, which are then tested for radioactive materials.

Both officials said there does not seem to be activity at North Korea’s missile launch sites to indicate missile tests occurring anytime soon.

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