The Korea Meteorological Administration said on Tuesday that a four-point-four magnitude seismic shock was detected shortly after North Korea's hydrogen bomb test on Sunday.
 
The seismic shock broke out at around 12:38 p.m., about eight minutes and thirty seconds after the initial five-point-seven magnitude blast.
 
The weather agency said that while the exact location or size of the cave-in haven't yet been confirmed, it is estimated to be about seven meters southeast from the nuclear test site.