On Wednesday, January 6, North Korea boasted about the “spectacular success” of their first hydrogen bomb test. Kim Jong Un stated on state television that it would “make the world…look up to our strong nuclear country.”

A lot of speculation from many countries say it didn’t happen.

At least the U.S. doesn’t believe it. The White House spokesman Josh Earnest said, “The initial analysis is not consistent with the North Korean claims.” Though it isn’t definitive, some experts are saying it’s possible a different, new type of bomb was detonated instead.

Norsar, a group that monitors nuclear tests, noted this and estimated that bomb would have to be less powerful than 10,000 tons of TNT, which is smaller than the bombs dropped on Hiroshima and Nagasaki. It is also significantly less dangerous than thermonuclear weapons that are equivalent to millions of tons of TNT.

The group also said that the test may have occurred underground, which would decrease or eliminate the amount of detectable radiation. Japan, South Korea, China and the U.S. are all testing for airborne and ground radiation. They have yet to find any.

“North Korea can bluff,” said David Albright, the founder of the Institute for Science and International Security. “It can claim that it now knows how to achieve high yields with thermonuclear concepts. It is difficult to prove it does not.”