UPDATE (1/6/16):

According to White House Press Secretary Josh Earnest, North Korea's claim that they had successfully conducted hydrogen bombs tests that resulted in a 5.1 magnitude earthquake is false, per an analysis from U.S. intelligence agencies. As Reuters reports, the White House is currently investigating the reported test but that initial findings are "not consistent with the claim the regime has made of a successful hydrogen bomb test."

See original story below.

After the United States Geological Survey reported a 5.1 magnitude earthquake 30 miles from Punggye-ri, South Korea's meteorological agency accused North Korea of conducting a nuclear test. That site had been previously used for such activity. According to the Huffington Post, Japan’s chief government spokesman also agreed that the quake was likely caused by a nuclear test and South Korea’s presidential office held an emergency security meeting on the matter.

"We suspect a man-made earthquake and are analyzing the scale and epicenter of the quake," a Korea Meteorological Administration official told Reuters.

Now, North Korea is saying that they were indeed testing hydrogen bombs and that the experiment was "successful." The announcement was made Tuesday night at 10:30 p.m. ET.

Per the Guardian, a hydrogen bomb, also called a thermonuclear bomb, is more powerful than an atomic bomb. North Korea’s supreme leader Kim Jong-un claimed to have said bomb in December but South Korea remained skeptical.

This story is still developing.