North Korea is suspected of carrying out a nuclear test on Wednesday after a 5.1 magnitude seismic tremor was detected near its main atomic test site in the north of the country. The China Earthquake Network Center described the quake as a “suspected explosion”.

The Korea Meteorological Administration told AFP that upon first analysis, the quake seemed to be a result of “artificial” causes, and the Japanese government said that there was a strong possibility of the seismic activity being a nuclear test.

The quake, which was detected at 10:00 am Pyongyang time, took place in the northeast of the country, right next to North Korea’s known nuclear test site at Punggye-ri.

Last month, North Korea’s leader Kim Jong-Un indicated that Pyongyang had already developed a powerful hydrogen bomb, though international experts doubted the claim. Researchers at the US-Korea Institute at Johns Hopkins University reported around the same time that satellite images showed evidence of a new tunnel being excavated at the nuclear test site.

The tunnel “adds to North Korea’s ability to conduct additional detonations over the coming years if it chooses to do so,” said the researchers at the time.

This would be the fourth nuclear test carried out by North Korea. Each previous test has resulted in international condemnation and tightened sanctions and restrictions against the country.

China, an ally of North Korea, has been pushing for a resumption of international talks aimed at finding a peaceful solution to the security concerns raised by North Korea’s nuclear weapons program. If Wednesday’s tremor is proven to be a result of nuclear activity, it would be a serious blow to Beijing’s attempt at renewing a diplomatic dialogue.